What we need is a technical schematic of the two mods :P
The only way to find out some of these changes is to play them both. Its going to be a challenge deciding what to keep and what to change for a fair combination of the two.
Good luck. I've only been running NYGM for a day, but there were a few problems already and few things that I didnt personally like compared to the personally selected mods I had before.
For me, the best option would be a combination of the campaigns from NYGM and GW, but leaving everything else an individual mod. This is similar to the way I had it, but I couldnt get past a certain point of the campaign with the unified vanilla campaign and didnt know how to fix it. As seen in
this thread