Factory audio controls after installing non factory amp???

I have a Non JBL with 3 dash speakers, 2017 crew Max

I looking to install a 4 channel amp, new component rear door speakers and new coax front door speakers,,,

I know that I can set the level of sound from these 4 speakers with the amp but how will the factory head unit controls integrate?

Example,,,,

If I set the amp and speakers up to where it sounds perfect to me can I use the HU Front/Rear balance controls to lower the sound in the back if my kids are back there sleeping?

I'm also not sure how the front dash speakers will integrate, with this,,,,,

Should I set the amp up the way I want it with the front/rear balance in the middle?

Am currently thinking of replacing the corner dash speakers and eliminating the center one. Will this mess with the way that the phone plays over the system?

am looking at the following,
rear- Morel Maximo 55-1/4" component speaker system
front-JBL GTO6296-1/2" 2-way car speakers

Those choices could change, I would like to use Morel Maximo 6.5 fronts but crutchfield says they would not fit