For speakers you're on your own deciding what to get, there is a never ending amount of speaker choices
But def component up front with coax in rear (you won't even notice the coax it's just for rear fill, rear components is dumb imo)
Also, if you plan on running a speaker amp you will need a separate wiring kit for the second amp (one power cable and set of RCAs for the sub amp and another cable and set of RCA for the speaker amp)
Unless, like already suggested you do a 5 channel setup. That would require only one wiring kit (one amp for 4 speakers and 1 sub)
I have personally never used a 5 channel I always run my sub separate but if you end up going low power route (we discussed 1000rms+) that would be the easiest way for u
I personally would find your speakers, install them and run them off headunit power for awhile then focus on getting a good sub stage, then work on a 4 channel amp for your speakers