I forgot to mention the deck was added on 2 years ago and has never been stained before

Not that I have heard of.

Buffing pads have grit. I would do a 60 grit then rinse with water when done.

what grid paper should i use and what about the prep needed after the sanding is completed...since i just stripped and brightened using RAD products, ...

We do not use a lot of solid stains but when we do we like the Flood solid stains.

The only thing you can do is remove and start over. You cannot add more to fix.

We use a floor buffer with a sanding pad. It can sand the floor in a few minutes.

I do not thin you can match Behr with any other brand that we have used.