I don't know but PC Game Wiki states Windows 7 as minimal OS requirement:
https://www.pcgamingwiki.com/wiki/Sir_Questionnaire

I also saw this, but given that the game small and the wiki page is sparsely populated, that information is probably pulled directly from the Steam page. So, it probably works, but I can see why additional confirmation would be nice. Perhaps you can take the plunge for the rest of us, Glq62.

What game controllers are the people in this part of the world using?

The new xbox controller, you need the drivers or update for the xbox one for it to work. It works with every single game I've tried.
I'm having a blast on every single retro 3D game due to using DSR with4% smoothing. I upscale my 1920*1200 to 3840*2400 which is perfect for home made remastered version. Due to the resolution being higher you sometime may need to increase either controller sensitivty or mouse sensitivity.

What I'm wondering is whether the DMC series works in win7. I know they do on the steam version, but I prefer gog.

Soulstone Survivors is compatible with win 7.
However, if you experience a crash when launching the game, you'll need to modify the parameter file in the root folder.

"Worshippers of Cthulhu" is OK with Win 7.

Kathy Rain 2: Soothsayer runs fine on Windows 7.
Kathy Rain: Director's Cut also runs fine.