Game won't start on Windows 10 x64

Probably in your Nerf.ini file (located in the system folder) there should be multiple settings for bots including "initial bots" which should be set to 5.

However, I also recommend using map-based bot numbers. If you open the console while in the match (~ key) try the command "botbalance". The console should reply with "bot balancing has been <enabled / disabled>". The goal is to enable it here and you may need to enable it for each gamemode you play.

Is OpenGL supposed to be any better resolution wise when compared to D3D? I've noticed that the zoom depth of field on the gun that is being held is much more zoomed in on a larger resolution but I wasn't sure if that is a D3D thing in itself. I was able to counteract this a bit by zooming out on the field of view. 

I think I need images to understand what you're asking. OpenGL has a number of rendering improvements and bugfixes. The D3D driver was also community-made but doesn't address every quirk NAB has and therefore still has some issues.