C++ & Perforce.
Large project usually will have separate temas of programmers… The core coders will provide base systems made in C++ and higher level system designers will work on derivative blueprints based on these core elements created with C++.
If lead organized pipeline well, then whenever a merge is needed it will happen in the C++ level, rarely in blueprint code.
Pure blueprint projects aren’t suitable for big teams, merging doesn’t always work…