As far as purely head to head I couldn't play on All Pro. There's a reason you can score 40 points in 4 or 6 min quarters in online ranked games on All Pro.
The game is tuned to allow bigger plays and more scoring on default AP.
When you play on AM head to head it tightens the game up in a good way. It also makes your CPU players on defense play better.
I don't notice any unrealistic boost when it's head to head.
As far as the CPU games go you just have to lower CPU sliders to try and even the playing field. I'd start with CPU QB acc to 25, pass block to 25, catch to 45, CPU run block to 30 or so. Maybe int to 25-30.
Just my opinion though.