PS/1s are basically generic PCs. No funky custom anything inside.
PS/2s are a whole different ball of wax. The hardware is horribly incompatible, using the funky (but at the time, technically superior,) MicroChannel architecture. They don't have a BIOS like modern computers, you had to boot from a special "Option Diskette" to make any hardware changes, including changing the amount of RAM! Which means: Do not remove a single piece of internal hardware from that machine!
The most useful versions of OS/2 (2.0 and later,) require a 386, so the Model 30 is out. (I had a Model 30 back in the day with a 386 upgrade card in it, and forced OS/2 2.0 to install on a machine that was really far too low-spec for it.) Really, on the 286, your best bet is MS-DOS 6.22 with Windows 3.11. If you can get a copy of OS/2 1.3, that would work, but it's not a very 'usable' OS. (Although Windows NT 4.0 still retained enough OS/2 underpinnings to be able to run OS/2 1.x applications!)
I don't know what the PS/1 Expert has inside, but a quick search makes it appear to be a 486. That, of course, should be able to run even OS/2 Warp 4 acceptably. (There are still people using OS/2 4 as a primary OS, and Firefox is still actively developed for OS/2, the OS/2 ports known as "Warpzilla".)