If its on Steam or GOG it will most likely run on Win7.
This might be the wrong forum section for such questions though.

EdmondDantes wrote:

But specifically I'm wondering if the following games will run on Windows 7: […]
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But specifically I'm wondering if the following games will run on Windows 7:

-Golf It (a game I've seen Mangaminx and Markiplier do Lets Plays of, there doesn't really seem to be an old-school equivalent. Here's a link to Mark's LP)
-Megaman Legacy Collection 2 (for Mega Man 9 and 10 mainly)
-Mighty No. 9

they all run on windows 7. BTW, Mighty No. 9 is hot garbage. I regret having paid any money for it. not even worth it on a deep discount. The only thing you can expect from it is disappointment.

EdmondDantes wrote:

Pretty sure both of these are on Steam. Does everything on Steam work on Windows 7?

generally yes. However, there are some old games that have issues beyond windows XP, which is going to be fun next year when windows XP support for steam goes away. Also there is a chance that there are DirectX 12 only games which would only run on windows 10 on steam, but I am not currently aware of any that have not at least a directX 11 fallback.

EdmondDantes wrote:

Alternatively, if I build a modern-ish rig I may opt for a Linux distro of some sort. Will the listed above games run on Linux?

I have no idea if the listed games run on linux ( my money is on no). Generally, linux support, while it has gotten better is nowhere near sufficient to consider it a usable gaming platform. Same applies to mac OS.

EdmondDantes wrote:

Also, is there any currently known "upper limit" to what Windows 7 can handle in terms of hardware specs?

Yes. Neither AMD Ryzen nor Intel plattforms from kaby lake on (7000 series) have official support for windows 7 (IIRC both are windows 10 only). While you theoretically can run windows 7 on either finding drivers that work, particularly for USB and storage is somewhere between difficult to impossible. Also, Nvidia has stopped support for any 32 bit windows versions, so if you plan on using 32bit windows any future videocards from them won' work.

You'd see mostly negative reviews about those games if they didn't (well except for MN9 which is another story like an anime fan on prom night)

mcobit wrote:

If its on Steam or GOG it will most likely run on Win7.
This might be the wrong forum section for such questions though.

Yeah I didn't realize that until much later, sorry. Just so used to posting in Marvin...

and yeah I've heard the negative press about Mighty No. 9 and watched several reviews... I'm seriously thinking if I go through with that one I'll wait for a price drop or a sale.

Really the one game that's really tempted me towards a modern rig is Golf It (and some other golf games which have been played on channels like Mangaminx's or JackSepticEye's, like Tower Unite Golf or Golf With Your Friends... all are very similar though, so if I choose just one it would likely be Golf It). Seriously, I got addicted just watching videos of other people playing, and I never even liked golf games before.