My wife is leaving her 2014 27" iMac behind. She had hoped to use it as a display in conjunction with a brand new M1 MBP, but, from what we can ascertain, that is not possible with MBPs manufactured after 2020. Also, apparently using an iMac in target disk mode is more problematic than going with a stand-alone display.
Any thoughts as to what current 27" displays would be a good choice to replace the iMac for this purpose? Also what sort of cabling would yield the best results?
When I set up my new MBP M1 Pro for desktop use I bought two of these monitors, two of these cables, and this hub. I have other peripherals beside the monitors, so the hub may not be critical for you (and it’s currently backordered on Amazon), but I can now go between mobile and desktop by plugging in one cable. Very nice.
+1 for that TB4 hub and the DP cable.
In principle, for somebody coming form a 27" iMac I’d suggest to get a 5K screen, but they’re really expensive and there’s still hardly any selection to choose from these days. TVs are 4K (or perhaps 8K) and that’s where the bulk of effort lies, so that’s what shows a lot of choice and has its prices driven down. No TV market at 5K.
So next best thing. 3840x2160 is the the natural 2x oversampling of the old-school 1080p resolution. While 1080p on a 27" is garbage (at least for a desktop computer) doubling it on a 27" just makes for very crisp text and beautiful images.
I’m using this Dell U2720Q and running it at 2560x1440 like my old pre-retina 27". Like all non-Apple screens this Dell is plastic, but it has very thin bezels and a fairly minimalist design so there’s not much ugliness you have to look at. The panel, however, is absolutely excellent. Bright and sharp, good color accuracy, no funny business. Along with full maneuverability (height, tilt, swivel, rotation), fairly intuituve and simple on-screen display options, and multiple inputs so you can connect several Macs (or PCs) it just makes for an all-around great display. I’ve always been very happy with high-end Dell displays (I otherwise can’t stand the company) and with this model again I’ve been very pleased (except for this minor detail).
Note, there’s also the U2720QM model, which is the exact same display but ships with HDMI cable instead of DP—I’m told M signifies consumer/home use and hence the different cable. But the rest is perfectly identical.
It would be really sweet if Apple released a 5K screen for regular/semi-pro desktop users. Basically an iMac without the iMac. Well, and some height/swivel adjustment. I won’t even dare ask for multiple inputs. When was the last time Apple ever did that? 
5K iMac starts at $1799. If Apple would sell the 5K display for $999, they should be making a boat load of money. I doubt the kind of folks whose work requires them to fork over $5k for an XDR would ever consider getting such a pleb screen instead. But $1k heading Apple’s way instead of $700 going to Dell should make Tim at al. at least a tiny bit giddy.
I think you’re the one who recommended them to me. 
The LG’s get good reviews as do the BenQ’s assuming you need the high fidelity color they provide. I’m considering replacing my 2019 iMac with an M2 mini or M1 Pro Max mini when/if it arrives for photo processing and those are what I’m looking for. Alternatively…I really want something that’s 5K or greater like the current Intel iMac is so that might force me into an iMac Pro Mwhatever or whatever it’s named instead as 5K monitors are a distinct price jump over anything not 5k.
I’m going to suggest an alternative approach to two screens
– one larger screen.
I had two 27" monitors for years – but the second monitor was always just a bit to the side – maybe just because I wanted one view directly in front of me, not both slightly slanted.
About 6 months ago I changed to an LG 34WN780-B UltraWide Ergo 34" 21:9 QHD IPS Monitor – which I actually got from B&H Photo in NYC with 2-day free shipping. It was $600.
I love everything about the change. The actual viewing area (at comparable resolution settings) is not much less than the two 27" but the area is all directly (flat-facing) in front of me, bright and sharp. For me that makes it feel like more area that is actually usable moment to moment. The whole desk area and landscape feels more open and less on top of me.
It comes with its own clamping desk mount that takes up absolutely minimal space – as well as a regular stand if you prefer.
It is not 5k – but I live in a screen of words > graphics and so as long as things are sharp I am probably less sensitive to fine shades or perfect blacks, etc.
Just a thought. There are many good monitors out there now, I am sure you will be pleased with whatever you decide.
Thanks for sharing this information. I’ve been thinking about an ultra-wide monitor for years, but I’ve been a bit concerned about how a Mac would work with it. I haven’t asked about it here, because I’m not planning to buy one any time soon, but since you brought it up… 
What model Mac are you using this display with? Are you connected using HDMI or DisplayPort? Did you need to do anything special in order to use its native resolution (3440x1440)? Does macOS see it as a retina/HiDPI screen? If not, do you care?
Comparing it with my current monitor (a 24" 16:10 display featuring 1920x1200 resolution), it looks like your LG’s image is slightly taller (about 13.4" tall vs. about 12.7" on mine), and the DPI is a little higher (107 dpi vs 94 on mine), so I think I wouldn’t want to enable any kind of HiDPI scaling, but I’m curious about what you think.
David
I will do my best to respond in adequate detail – remembering that ultimately monitor assessment is visual and so a bit subjective.
I have a Mini M1 (bought Dec 20200 and used it first with the dual 27" and now the 34’
I am connecting by HDMI to HDMI
the Display function in System preferences is at “Display Default” as confirmed when check "scaled’ which allows you to adjust to other resolutions
– I have had to set the default scale in some applications to >100% – but that has more to do with my eyes than with the monitor and is very simple to set so it is not a recurrent task.
You cannot do HiDPI on this monitor
– going to that more than doubles the price and was not one of my options.
My prior 27" was a ViewSonic VX2776-4K-MHD which was HiDPI
– I had to scale that down to be readable system font and icons
It was beautiful and sharp – but did not solve my issue with two monitors as detailed above
I am far happier personally with the larger functional area all being directly in front of me
– and the resolution is just fine.
the color and sharpness is outstanding
Hope this helps
I’ve long thought about an ultra-wide monitor too, though having at 27-inch iMac with a 5K Retina display makes it hard to consider anything else. I’ve kept with a 27-inch non-Retina Thunderbolt Display for years because of it. But I could imagine switching to a Mac mini or Mac Pro (if there’s a mini option when the M-series version ships) with a single monitor if it was good enough.
I do agree that the edges of two 27-inch monitors are now (as I’ve gotten older) quite a distance away, so less width wouldn’t be an entirely bad thing. But I’d still like Retina so my text is perfectly crisp—I can really tell the difference on the Thunderbolt Display.
I have a 3-monitor setup (a 24" and a 27" hooked up to my old 2010 Mac Pro, plus an old 27" iMac with 5K screen) – awkward as hell, fills up almost my whole large desk. In fact currently the iMac isn’t even hooked up; despite its gorgeous screen, I stuck it in the closet for the moment.
I’ve wrestled with the tradeoff between high-DPI, which is best for all the digital drawing/painting I do, and a lower res, which is best for everything else I do (easier to read the larger type, etc). What I’d really like is a hybrid huge screen where the system knew which windows belonged to which applications… and set the art windows to hi-res and the other windows to lower res, simultaneously on the same monitor. AFAIK that’s impossible, but wouldn’t that be great?
Screens are very low profit margin products:
LG Display net profit margin as of September 30, 2021 is 5.74%
https://www.macrotrends.net/stocks/charts/LPL/lg-display/profit-margins
And the market for displays has been flooded for years.
LOL. So are smartphones overall. Apple still manages handily.
Apple’s hardware products are drastically different and distinct from their competitors. That’s why they developed the Pro display. Rumor has it that Apple will announce an upgraded Pro screen and desktop shortly, as well as a not terribly lower priced monitor.
In January of 2020 I bought an LG 32UK550-B 32 Inch 4K monitor that I have been very happy with. At the same time I bought a Mac Pro (2019) tower. They are attached using HDMI. The resolution is set at 3840x2160. This monitor has given me no problems.
My profession is computational physics. At times I have had 11 or 12 Fortran programs running simultaneously on this Mac. Some calculations took days to complete. The results were analyzed using lots of large, high resolution graphics. Recently I retired. Now this system seems large and over kill, but I still enjoy the sharp LG screen.
My experience is that connecting an iMac to another Mac doesn’t require “target mode”, and doesn’t require using the iMac as though it were an external monitor (not possible in my case, my iMac is too old).
What I do is simply connect both Macs to the same router with ethernet cables, use an account with the same username on both, and turn on sharing on both. Each Mac sees the other one in Finder, and is connected to the same iCloud account. Not ideal perhaps, but the integration is almost seamless and I find it quite useful.
I am using a 27inch HP Z27, and I would recommend it. Plugged into M1 MacBook Pro 13inch, and previously with a 2016 15inch MBP, both via USB-C connection.
What I like:
Cheers.