Help me plan out my wheel+tire sizes. Do I need a full-size spare too?

I've got a stock 2020 TRD OR DCLB that I'm planning on giving a ~2" lift with the Old Man Emu medium load kit.

Wheels
Once the lift is done, I'm looking at a set of 16"x8" Fifteen52 Turbomac HD Classics. It looks like I can choose a back spacing of 4.5" or 4.75".

Tires
For tires, I'm considering BFG KO2's or Falken Wildpeaks.
I know this question has been done to death, but I've seen discussions that these various sizes can fit without any rubbing:

• 275/75/R16 (32.2")
• 275/70/R16 (31.2")
• 265/75/R16 (31.6")

265/75/16 seemed to be the safest bet, although I'd prefer the extra height (.6") of the 275/75/R16 if that would work.


Questions

1. What backspacing should I choose between 4.5" or 4.75"? How will that affect rubbing and tire size?
2. Knowing the backspacing of the wheels, what tire size should I go with? I'd consider myself a weekend warrior, driving mostly easy forest service roads, but definitely have spots where I have to do some rock crawling. If this is too difficult to guess at over the internet, should I bring the wheels to Discount Tire and have them match and test in person?
3. I'm used to AWD cars where all the wheels need their treads matched and a full-size spare is required. Should I get a fifth wheel and tire, or is the stock wheel under the truck sufficient?