How small do they need to be, and how powerful? Also what kind of budget? ($500-600, or 800-1200?) And how many machines?
I would strongly recommend getting a case that can take MicroATX. They are not much bigger than ITX, but they are a lot cheaper for a fleet ($50 cheaper per board). Maybe SGPC K88 (chinese case maker) has a model that would work.
(If you need really cheap, I would almost suggest an Omen 15L or the OEM HP variant and get a bunch of $97-130 RX5700XT.)
If you don't need a ton of GPU horsepower and an RX 780M integrated GPU would work the Beelink SER7 7840HS looks pretty good.
Minisforum also has a sale on Ryzen 7 machines; the 6600 mobile HX77g is $619 barebones with the recent sale.