If you're happy with hicaps stick with the G&G mags, they're fine but the mids have been a bit sketchy.
The blowback is just a rattly flappy plate on the gearbox which makes a noise but if you ever need a new gearbox (say...when the front cracks off) then you either buy a standard gearbox and lose the flappy clacky bit or pay through the nose for a new G&G box.
Why though are you "trying to avoid LiPo as much as possible"? They're not inherently dangerous as half the internet seems to want people to think and if you stick to 7.4v they won't lunch your gears or trigger contacts terribly quickly either.