PLA6456, 2 pairs as a LAG?

I've read that multiple PLA networks on LAN, or single subnet don't interfere or degrade each other even though I would think it would.  I installed my first pair to an outlet I installed to the main electrical distribution panel, on its own beaker which shares the same bus blade as the 100 amp breaker that feeds the garage which is where the other PLA adapter was installed.  FYI, there is a Leviton panel surge connected at this panel on its own 2 pole 20amp breaker.  I installed the other adapter in the garage and tested on each phase of that sub panel but the best speed I could get was about 80 up & down on a 1gig symmetrical service.  I was hoping for over 100mbps, ideally even higher.  It's maybe a 200' of 100amp sub feeder cable run to the garage with no connections between and nothing noisy in the garage.  Nothing even on when I tested so it could be worse when lights and other stuff is on.  So long story short, if another PLA network won't interfere does putting a 2nd pair in to make a LAG group make sense?  I've been thinking about just using direction antenna and a wifi bridge but that's considerably more money, just a single antenna costs more and I'd need 2 with compatible APs, $$$.  I have a GS-1350-12HP in the garage and an XGS-1930-28HP in the house.  Should I trust these PLA devices or just go with the wifi bridge.  I'm gonna need 4 cameras and an AP in the garage, cameras will only need roughly 20mbps as long as they stay 1080p but I can see 4mp or 8mp down the road.