Saving as a folder-based project and using source control software should work well. The main problem to watch out for is as 
msv0001 asked - if you edit the files wrong, Construct 2 might not understand the project any more. Some features require that if you change something, other things corresponding to it may also need to be updated. It's difficult to document all of these cases because it's a large and complex file format which also changes fairly regularly too.
Generally try to use C2 to edit projects wherever possible; if you resolve conflicts and merge everything correctly, it should always work. If you get a conflict and don't merge it properly it could break the project, but then I suppose the same is true of most source controlled things... you just have to be careful!