I tried turning on ADP. It turns out you’re not allowed to if you have back-level devices attached to your account. In my case, that’s a Mojave virtual machine.
I first had to turn on a Recovery Key (but I thought I already had one, that is shorter than the new one??). Now I’m wondering if I should leave it on or turn it off. I’m thinking back to last year when Apple had a problem and all of my devices were no longer trusted.
I’ve had ADP turned on essentially since it became an option. I have not experienced any issues with it so far — at least none I’m aware of. Safari iCloud syncing is a mess (mostly iCloud tabs, sometimes also bookmarks), but that was iffy even before ADP as far as I can recall. I did have to throw a whole bunch of older systems overboard to get onto ADP, but since they mostly didn’t really rely on my specific AppleID that didn’t come at a huge cost. I just put them on a secondary AppleID I set aside for legacy systems.