As for "universal" bracket, I required only one point to fix my holder, and the very first design in this thread has two holes for mounting (will take any Ram-Mount accessory that uses the diamond base 2 hole pattern).
The second design with more holes for mounting on top of it allows to fix more types of RAM mounts and not only RAM. For my case it allows to chose whether to fix holder with some offset or directly over the accessory bar. There is no specific use of the big hole in the center, but you can put a wire through it if suitable; that's just by design, I believe, for saving some material, whilst keeping the strength sufficiently enough.
The second design with more holes for mounting on top of it allows to fix more types of RAM mounts and not only RAM. For my case it allows to chose whether to fix holder with some offset or directly over the accessory bar. There is no specific use of the big hole in the center, but you can put a wire through it if suitable; that's just by design, I believe, for saving some material, whilst keeping the strength sufficiently enough.