Sundial - what type of cranks do you need? triple or double or compact double?

I've got a few spare 165 mm cranks and a 170 mm or so.

I'm 5'1, maybe a 29 inch inseam and use 165's (I can manage with 170s, but like 165's better) - BF is 5'7 with a 33 inch inseam, he uses 170's

Mountain bikes typically have longer cranks than road bikes.