"give the once-over" is wide term.
My suggestion is to check each item going price on eBay. I have some cameras from OP Pandora box before. Many of them are far away from flea market 5$ cash and go.
So, check it on eBay. If it sound promising, get on-line manual for the camera. Mamiya, old Graflex SLR and monorail camera manuals should be available under Google search. Read and understand the manual. Try to operate camera, lens. See if it works. Works or not, I'll just stop where and sell it as is with description like : not tested with film, checked this and this and it works like what.
If me, I would try to check with film Mamiya kit and Monorail. And check Minolta light meter if it works. This one doesn't looks like cheap one or retro like others (usually dead or inaccurate by now). I'm not sure if TLR is easy to check without film. At least frame counter is not going to work. Monorail could be checked just by its focus glass on the back (if it still where).
TLR is the easiest to check, because it is 120. Easy to develop and scan. Monorail could be 4x5 or larger, might have correct film holder or it might be none. If OP has all for developing and scan it makes sense. If not, stop at the phase one. Manual, read, try without film and sell.
Folders might have light leaks in the bellows and gunk in the lens. They might be also not for 120 film. Small old 35mm cameras, most likely are going to have not working shutters and gunk in the lens as well.