Too many rights because of BUILTIN\Users Group. Please help.

Hello to everyone!

I'm facing this issue and need your help guys. I have Windows Server primarily for hosting web sites. Well, now some developers need to access web root folders to run web based commands like composer install etc. For this purpose I have installed SSH server so they can access their web folder and run those commands. 

Problem is that every user I have created belongs to windows built-in users group which has access to almost everywhere! C or D etc. They can even write anywhere they want. I tried to remove them from USERS group but they still belong to BUILTIN\Users group and still able to see and write to unwanted folders.

So my main question is, can I just remove Users Group from these disks or this may lead to serious problems?

Or, is there an option to isolate these users leaving this group untouched?

Thanks!!