There's a whole list of USB webcams compatible with mjpg streamer though this list is only updated if someone feels like adding their webcam, it is not comprehensive. All Pi cameras also work with mjpg streamer as it is setup in OctoPi or manually following that guide.
'Which camera to buy' is a difficult question, since there's lots of different factors - price, quality, mounting, compatibility, features etc. You could say that a $100+ 4K UHD webcam is the best to buy, but obviously that's overkill.
The pandemic also changed things, with webcam prices doubling in some cases. Now, a Raspberry Pi Camera is a more attractive option, since it can't as easily be used as a webcam it's price didn't change much. Lots of people use this with success.
So many people use so many cameras, there is not one 'This is it' camera.
TL;DR; Choose a webcam that fits what you want it to do.
If you find a model but are unsure if it will work, we can probably take a guess. Other than that, it is up to you.