While I don't use github for multi users, I would advice that you avoid relative module paths and copy all modules locally to the project folder.
This makes sure everyone has the right file setup and the same files that are up to date.
this wont work for B4X projects, but you still have the same problem if everything is in the root folder.
the main problem is how the "meta" data is saved inside the actual project file. There are always parts wich github cannot merge automatically, even it was a simple task. So we always need to fix the merge manually, wich costs a lot of time.
Of course we always use branches, and if its working we merge into the main repo.
Were working with Visual Studio in the past without any problems. (Besides it already contains a full git integration and Teambrowser)
I will open a post in the Wish section. I think for the future a good git compatibility is very important since the community is growing and growing.
Also with bigger companys.
In our company we now working on a heavy and big project in B4A. It already contains over 200 classes and it will grow further.
But we working with 5 People on it on different branches at the same time.