My recommendation is to try and first find others with aftermarket in-dash systems and look at the actual screen while in the drivers seat. Everything looks good in a display or pictures but can be a whole other thing when mounted in a fixed dash and being looked at by you from your seating position.
I use a Android based navigation system that is mounted on top of the dash. This allows me to adjust the viewing angle regardless of whatever light or reflective condition exist. It also allows me to double up on other Android based apps for the RV such as the TPMS, gas buddy, etc.
As for the cameras, since there is no inside rear view mirror, I had a monitor mounted in that spot for the cameras. While driving, I found it to be a more natural instinct to glance up at the monitor like you would normally glance up at a rear view mirror. With the side mounted cameras, when I use the right turn signal the monitor splits the screen rear/right. When using the left turn signal, it splits left/rear.
