Just go 4ohm all the way around. 2ohm is fine for a sub but you sacrifice too much sound quality to use them in a coaxial setup. The only reason to go 2ohm is if you are going to wire two 2ohm speakers in series to get 4 ohms. And if you need that many speakers you're going to get better sound quality and adjustability by going to a 6 channel amp.
Skip the 4" in dash speakers in the front. The size of them limits them to high frequencies and those are directional. You get very little benefit from them for the cost cause they basically point right at the floor, so all the sound goes there. If you want more highs up front you're far better getting a component system and getting a tweeter mount from Solvefunction. If you insist on keeping the in dash, and don't want a 6 channel amp, then rewire everything to have them be in series vs parallel.
If you're going through all this work run new, larger, high quality speaker wires from your amp to your speakers. The factory wiring in undersized for the kind of power you'll be running and it will reduce sound quality. It's also unshielded so you get more interference.
For speaker brands consider Hertz. Their shallow mount 6.5inch
Hertz DCX 170.3 Dieci series car audio coaxial - https://hertz-audio.com/product/car-audio-coaxials-dieci-dcx170_3-2/ worked great in the front door of my LC. No spacer needed, just installed it on top of the door card. They sound really good too. I went 6.5
Hertz DCX 160.3 Dieci series car audio coaxial speaker - https://hertz-audio.com/product/dcx-160-3/ in the rear but had to run a spacer and cut some sheet metal. I did not care about keeping the factory look so I used the old school mesh grills. I may paint them to match someday but the black looks fine.
I used a similar 4 channel Fosgate amp for mine. It was designed for UTV use so its small and it fit in the space where the factory amp used to be.
Can't go wrong with Fosgate for a sub amp either. I've since moved away from building big systems, but I had a punch gold series amp that lasted over 20 years (may still work for all I know it went with my last truck when I sold it).
I believe the factory sub location is 6". Honestly its not worth the time and money to put that size in there so if you're going to do it go to at least 8" or even 10". There are a number of write ups on how to build a box for the factory location. This has been on my to-do list for a while but still haven't gotten around to it.