It's safer to stick with the standard 8.4V but lipo's aren't that much more of a burden to take care of just don't be retarded and use common sense coupled with extensive pre-reading about them.
As for blow back on an AEG screw it, it's just a piece of metal that moves back and forth and really weak at that. (Exception being the TM Electric Blow Back system and the Modify Tremors "upgrade" kit that provide more blow back but still kind of weak).
As for AV it's definitely worth it, even if you don't buy since at least you get the option of shopping around and comparing classifieds vs retail/public stores.
Also airsoft is like paintball in many regards, hell we use some of the same equipment. But be warned airsoft requires a heavy investment on the front end but BB's are cheaper whereas as you already know paintball is relatively cheap to start (not considering Palmer Customs and such) but paint is killer.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE