you can edit most default properties with the console. the popular code "set pawn drawscale 2" would be an example for it. you set the value of the drawscale of every pawnclass to 2. the command which allows you to run fast would be something like "set pawn groundspeed 4000" but i guess they've just used a higher serverspeed.
you could do exactly the same with pickups. "set dc17mAntiarmorweaponpickup inventorytype none" would disable the antiarmor.
for the sniperammo they've used most likely something like "set dc17msniperammo maxammo 99".