There are lots of "electrical" considerations.
The TFT backlight takes 100mA - 300mA.
The 12V USB converter is probably going to be buck arrangement.
A linear chip like a 7805 will waste a lot of heat.
Ground loops in automobile wiring might be noisy, damage chips, ...
I have never attempted automobile electronics. There must be lots of Application Notes, Tutorials, advice ...
David.