I wouldn't buy paddles for Pismo (unnecessary), but for Glamis sure. I would get a full sand tire set and offset the rims for stability. Stock xp1000 feels too tipsy in the big dunes pro R is already wide though so I'm but sure. That said, you can dune with stock wheels just fine if you know what your doing and if you lower the pressure but sand tires sure are nice. Get something light weight, and don't worry about scrub radius etc. Been running 5-3 offset fronts for years with my sand tires without any issues with ball joints etc. The extra stability is worth it Can't go wrong with STUs or 30" skats, but there are other options. If you over paddle, or go with cheaper heavy paddles you might regret it. Also good tires will be easier to sell later should you need to.
Beadlocks are cool, but not necessary for sand tires and will result in extra weight.
Not familiar with the 360s.
The Pro R should do fine with stock, maybe just run the stock setup and check out what others are running to get some good ideas.