For the PC I would recommend Lake County CCS pads. For correction of swirls and scratches I would get a 3 1/2 in backing plate and some 4" orange pads, maybe a yellow just in case for a more difficult job and some white and blue pads for finishing and applying wax/sealant. I have found the bigger 6 inch pads don't do much correcting. A good polish like the Menz line is what I use and works great for getting rid of swirls/scratches/water spots, etc.
Unless you detail for money or have or will be detailing alot of cars that have alot of bad defects I don't really see the need to spend all the extra money on a Flex which costs over twice as much as a PC. If you are just getting something to polish your black G35 the PC7424 is plenty and will be more then enough to keep it looking great and will give excellent results. I have a black Lexus and also detail my parents black Acuras and the PC has done an excellent job getting rid of scratches, swirls, water spots, etc and I never needed anything more, a Flex maybe faster but it is no big deal. A PC with a 4" orange pad and a good polish like Menz IP will take care of pretty much any of your common defects unless they have really bad which would require wetsanding. If I decide to detail for money on the side I might step up to a Flex but for my own car and occasional detailing of my parents cars a PC is more then enough and I am very happy with it.