Hey there! I’m currently installing Endeavour on my X220T. I’m actually in the live boot right now, waiting on it to finish, so I can boot into the actual system. I currently use Manjaro on my T420, anything different that I should expect?
Less stuff preinstalled, quite a few packages you might expect in the repos will actually have to be installed from the AUR, more terminal-centric but also with a LOT of support in these forums.
Also the obvious, obviously: Far more common updates since you are now on Arch Proper, so you’ll get update notices about something basically every time you start your computer.
Edit: and welcome!!!