wiring ideas for power port and future addtions

im upgrading to a 04 precedent ( from an 01 ds)

i've searched but cant quite get my head around what i'm trying to do.

i want to add a usb power port( charge phones, etc). and am thinking about running a aux fuse block & switch to power it off of, so i can then also allow for future additions.

do folks put the fuse block in the engine compartment or in the front dash compartment.

also, it it preferred to run these accessories of the key switch?

thanks for the advice.. im taking delivery in a week and want to get my wiring parts in before hand.