Your going to get lots of opinions on what is best. It really all comes down to what you want to pay. With this sort of thing, you get what you pay for when it comes to sanders. Hutchins is top notch if you are willing to dish out the cash. But I've been using a farm hand brand from Tractor Supply for years now with great results. (for 80 grit only). I seldom use the da after my first coat of primer unless the customer is wanting "cheap work". You will find that hand sanding with various shapes/sizes of blocks will always give better results.
I found a snap on palm da that I use with a soft backing pad (A MUST FOR CLEAR COAT CUTTING) and it has worked fine for me. Although I've used many other brands that gave the same results but only lasted a year or two. (Harbor Freight comes to mind).
As far as paper goes.. I stick with 3m, Summit Racings shop brand (cheap), or whatever I have on hand. It doesn't really matter what brand until you get to the clear cutting and buffing imo.
also... don't expect to use a da on the entire car for cutting your clear. There WILL be lots of hand sanding that will require the use of different blocks also.
You may have known all of that, but I thought I'd tell you just in case. The most important thing about prepping a car before you paint is the use of guide coat. If you have never used it, or would like to know how, just ask.
Lots of guys on here (including me) would be glad to give you some pointers.
Hope I've helped