Just curious if I'm understanding correctly: So this one says 18W each port and QC 3 certified. But on Samsung phones it won't accept more than 10W because only Samsung chargers will for their own branded phones? And using this on any other phone that has QC3 will charge at 18W?

This is similar to the car adapter I used: https://www.amazon.com/dp/B07XJTT9WG/ref=cm_sw_r_cp_apa_i_E0y1DbXBSX95H

I also had to search for USB extension cables that had to have a short plug so that when I put the storage tray back, it doesn't kink it too much. Other than that I ran the cables exactly the way you did.