What I was thinking was P21S PCL x 2, AIO x 2
~ Again, these 2 products' main function is very similar: they're good cleaners. Also keep in mind, these are not products that layer due to the fact that when you apply the 2nd layer, it's cleaning abilities will remove the previous layer.
I was wondering if I should replace P21S PCL with #80. Would it do a better job of hiding the remainder of the imperfections. The car I am working on has maor of swirls.
~ If you need to remove swirls, you need some kind of polish or compound to do that. #80 is a polish that will be able to take care of some swirls. Because it's an abrasive, it will actually remove some of your swirls. If you're looking for a product that fills in the swirls, then you want some kind of glaze. Because the swirls are not actually removed, once the glaze wears off you will begin to see swirls again. A glaze can also hinder the ability of your LSP to bond properly to your paint (this is why K-AIO is recommended before SG, to insure the cleanest surface possible for the sealant/wax to bond properly).
Should I expect to get the hood back to perfection (swirls, maring, or light scratches) with a PC or is this too much of a hope.
~ That varies on the hardness of your paint/clearcoat. I personally would not expect perfection from a PC. There are some scratches that even though it doesn't go down to the primer, they're so deep that you're better off living with that scratch on your car instead of risking the chance of taking too much clearcoat off in pursuit of removing that scratch.
Just because you see people post pictures on here of an almost perfect finish doesn't mean that's always the case. Pictures can be very deceiving. Especially if this car you're working on is a daily driver, it'll get scratched and swirled from every day use and weekly washes/drying. I'm not saying perfection isn't possible, but just don't go crazy thinking it has to look 100% perfect.