I have used these pads as you intend to and had issues with them getting cut by the edge of the 3.5" backing plate. You will see it after doing a few panels. Not that they don't do a good job, just be aware.
I just did this for the first time about a month ago. I used the 3M kit. The lights came out great. You must get all the film removed until the lenses are crystal clear. I sealed them with 2 coats of FK1000P but I've read in some thread that helmsman spar varnish in a 50/50 mix with odorless...
I am relatively new to machine detailing. I first purchased the PC, did 2 vehicles and ordered the flex. I am very happy with both. I still use the PC for tight places with smaller pads and it is invaluable for that task. I'd recommend you start with the PC and see where it takes you.
LAst winter I used WGDGPS 2x and a coat of fuzion and it made it through the winter on garage kept daily driver.
This winter I'm planning on FK2180 topped with FK1000p
I've used it. It's more than a QD or wax. It last much longer. I still prefer a good two step polish, sealant and wax job. I continue to use wetpaint on all the exterior glass.
It takes a while that's for sure. I got a flex to solve that problem and use the pc with 4" pads for the tighter spots. The flex cut the polish time because it corrects quicker and uses 6.5" pads.