Simple, really.
In normal law, pitch command is blend of rate+G, roll command is roll rate. It doesn't feel awkward, I have quickly adapted to it and equally quickly forgotten it, once I was back on classic controls.
Simultaneous inputs form both sides are actively discouraged during training. If they are made, both inputs are simply summed and result passed to flight control computers, limiting value being 100% displacement. E.G. both full left sidesticks give maximum left roll rate command that is achieved with one sidestick in neutral and other fully deflected. If sidesticks are displaced at the opposite ends, sum iz zero and no command is given to FCCs.
When practicing incap in the sim, procedure was for the pilot simulating incapacitated pilot to push stick fully outboard and forward. Pilot taking over would have to press priority button and correct the attitude,. if he forgot the appropriate sequence and used dual input to stop the excursion, nothing much would have happened when the priority finally got pressed. Both controls and aeroplane have a lot of inertia and G-protection would prevent excessive load anyway.
IIRC, if one stick was latched out by holding the other takeover button, it could be restored by pressing its button, not any.
Oh, and PIC = pilot in command, independent of who flies. The gal/guy that handles the aeroplane's controls is PF(lying) or H(andling)P.