AK...Real Sword, we can't link
pistols are depends very much on situation...like if you use an AK ( which I had before), I pretty much have to sling it to my side when entering a room and take out my pistol. Not only pistols move around easier in rooms, also I want to make sure I'm not shooting someone point blank with a 400FPS gun. (no MED at that time)
Also for bb capacity, I suggest use 100-120rd Midcaps for the best balance between "realism" and usefulness on the field. I used high caps last game because I ran dry and a teammate offered me one. I couldn't sneak up to people anymore because of how much rattle it makes...
IA M9? I searched it, and it returned KWJ. I think it's the same M9 that I use. Not worth 100 bucks used. If it comes with a bunch of mags then sure, but no..I don't think it's worth it. I bought that M9 new for $109 and $25 on an extra mag..
PS: I personally do not like AK's reloading where you have to clip the mag in then swivel the rear into the mag well. I can reload a M4 mag style much more faster than AK Mag style. (even tho I only changed to M4 platform recently)