I will be getting the PC 7424XP and I am completely overwhelmed by product and accessory choices. This will primarily be used on my ingot silver 2011 and my wife's new TSX which is a darker shade of silver. I understand from my reading 5.5" pads are the way to go. My main questions are:

It seems there are 2 backing plates available, a black one and a "flex" yellow one. What is the difference, if any?

The black and yellow plates should be virtually the same....I'm partial to lake country backing plates and pads. Just be sure and buy a plate that's an inch smaller than your pads. That way if you do slip off of a panel, you won't be cursing because the spinning plate dug into your paint.

which foam pads to get as far as thickness (7/8", 1.5") and color (texture) ?

The better corrugated pads are going to be 1"-1.5" depending on brand. Color coded pad cut ratings will vary per manufacturer.

How do you approach smaller areas such as the panels around our taillights?

The smaller areas really need to be approached by hand. From my experience, if you try to push the pad in to reach such areas, you just end up pushing product in between body gaps, or between the lights and body.

Are bonnets nededed? Are they just for removal of LSP?

I've never removed LSP with the machine, so i can't say. A lambswool bonnet is worth a shot.

what polishes are best for new cars? I need nothing more then a very light cut. There are barely any imperfections other than some swirls on the acura. I am thinking poorboys world pro or meguiars 105. I also already have some meguiars #9.

Since your new to the PC, though the learning curve is pretty quick, I would be looking for mild swirl removers/polishes.....in your case a comprehensive polish/glaze might be all you need @ this point. I'm partial to wolfgang stuff. I'd get on autogeek.com........read read watch watch. That will mitigate much of the learning curve, and then pick products that advertise long working times.

Are the machines good for wax application or is hand application better? And if so, liquid or paste?

Machine application of any product whether it be corrective or LSP is going to spread/work the product far better than any human can accomplish.
Sorry so many questions, but...

Thanks!

Clay the car first before you start........you'd be surprised what clay pulls out of a new car's paint.. It's the least time consuming thing I do to paintwork, but it really shows when you're finished. Tip-keep your pads slightly damp with a periodic mist of any quick detailer.