OK, here goes. I currently have a deck with Thompsons WaterSeal Cedar Semi-Transparent on it. We power washed and stained a couple years ago, but it s...

It would be best to remove this all down to the bare wood. Strip off what you can and then sand the rest that does not strip. Brighten the wood after.

Best to prep with their Gemini Restore Kit and then apply a might maintenance coat of the TWP stain.

You should prep better. Use the Restore A Deck Stripper and Brightener Kit with pressure washing. This will even out the appearance so you can use a p...

I'm reading conflicting information everywhere. Some say strip, power wash, sand. Some say strip only. Some say sand only. I'm really confused. I do u...

They cannot contain both. Use a proper prep of a deck cleaner followed by a wood brightener.

No need to sand, just strip and brighten. It is not a hardwood.

Also, Is pressure treated pine considered a 'hard wood'? or can I use any stain on it?

Ahhh o.k. Glad I didn't order a softwood stain before knowing. Does it being PT make any difference in sanding it? Should I pressure wash it?

It is pressure treated pine. Your plan of action will work on this.