I just got one of the really nice MacBook Pros. Migrated from my 2015 MBP 15” (pre-butterfly, so I missed that altogether - my brother hates that keyboard, my son doesn’t have any problem with it). I used Migration Assistant via wi-fi to migrate the data, which, of course, said above the progress bar that it would take 9 hours, then 2 hours, then 6 hours…like all progress bars. Actually took 4 or 5 hours for about 800 Gb of stuff.
Having just read about artwork problems in Music app after upgrading to Catalina, I was glad I didn’t upgrade the old computer to Catalina and instead migrated to Catalina - I looked up Music artwork because the new Music app sadly doesn’t display the artwork in the left-hand column, but unlike upgraders, at least my artwork is still there.
The one prep thing I did was to locate and use MacCleanseX to dump a large proportion of the 32-bit apps on the old machine - I was surprised how few I still had. The only two I’ll greatly miss are TexEdit and Classic Menu. I’ll especially miss TexEdit - I discovered I now have no word processor that allows me to select a section of text and change the font of only that section, even BBEdit to my surprise changes the font of the entire document. This leads to the only migration problem I’ve had and which would solve the above problem, which I suspect is more Microsoft’s fault than Migration Assistant - stand-alone (no MS 365) Microsoft Office16 claims to be unregistered and insists I need to buy a copy; even though I have a registration code for it, I can find no way to enter the registration code.
I have the new machine hooked up to a Samsung 4K 27” monitor via an OWC Thunderbolt 3 dock with a MDP > DP cable, and it seems to work fine. Though it took a very long time to recognize the MB Pro initially (like a couple of hours - I thought I’d need tech support), it’s worked without a hitch since then even when disconnected from the dock and reconnected.