New stereo install questions

Question 1: no need to separate them down each side. Down the passenger side is fine, wire loom is suggested.
question 2: is a matter of choice, I have an inexpensive set of RockFord Fosgate 6x9 Coaxials rated at 200watts that I purchased for under 100.00 and can be mounted either way . Over or under the package tray.

Good Luck.

Bruce