32 hole would be sufficient.
You could use a regular hub (non-SS specific), easier and cheaper to experiment with gear ratios until you find what you like.
Shop around for the light 29er wheels. (merlin, crc, stw)
Crank length depends on many factors, height, inseam, whether you like to spin.
Shimano deore cranksets are great vfm, even 2nd hand.
Welcome to the obsession of bike building….