Am I right in thinking that I can run SRAM 11 speed shifter, mech, cassette and chain with a race face narrow/wide ring and race face cranks.

I don’t need to buy the expensive SRAM crankset with the weird BCD do I?

Correct.

The SRAM cranks aren’t that expensive though, and it’s only XX1 that has the weird 76mm BCD, the X01 cranks are the same, just a different spider. Lightest combo is with a spiderless ring anyway.

you can use any crank. I’m running an X0 crank with a raceface 32t and xx1 everything else

thank you