WAFM- I think it is weapons advanced flight modeling, which is partially incoporated into FC, and will be in BS on most if not all weapons. Of the ones listed and not explained i dont know what ATM is...
I think you thingy you were talking about was a collective, acts like the throttle on a fixed wing aircraft but is instead in a heli. You dont have to have one to play BS, but like a track IR or hotas it is something that might be helpful/realistic/fun. I depends on what you want and what you can afford. Urze is planning on releasing one when BS comes out that will fit onto the x52,x45,Cougar just to name a few. I have never used one, but i think it will be worth the money and looks fun.