I am not Roger, I am sure he will chime in, but I will give my opinions none the less

1. I would stick with the cross hatch method. When I got my first clay bar I posted on another forum (forgot, was long ago) there was a detailer who trolled there and gave lots of tips. He recommended cross hatch for almost all application of car detailing. He gave me a long technical answer which I cant remember (sounded good at the time) Since then I have read several detailing handbooks and most refer to this mether. I have used it since and havent been more happy.
2. Yes you still need to polish. Claying your car only gets rid of the nasty contaminants that collects on your paint. Smog, waterspot, brake dust....etc etc from the the environment. Polish actually reduces swirls, scratches and other blemishes.
3. for the wax you have to wait for Roger for the meguirs stuff

I have only used Griots for years. I use the best of show but since have purchase the pure caranuba wax...have yet to apply.