My 2017 Suburban Premier should be the same.
So you've set the seat, mirrors and steering wheel positions for FOB#1 and differently for FOB#2
You should have also set the exit positions (were you want to seat and searing wheel to move when you turn the truck off)
Once these are all set this is how the personal setting are going to work.
You (FBO#1) you unlock the door and hop in the truck the seat, steering wheel and mirrors will be still in the exit position, once you start the truck everything will move to the positions assigned to FOB#1.
You turn off the truck and open the drivers door all three will move back to the exit position.
You wife drives next (FOB#2) she'll unlock the door hop into the truck, again seat, steering wheel and mirrors will be in the exit position.
She'll start the car and all three will move to the positions assigned to FOB#2.
She turns off the truck opens the drivers door and the three will move the the exit position.
I hope that helps and clears things up