I posted on this thread awhile back. I run 165mm cranks on my gravel bike and 175mm crank arms on my road bike. I'm 5'7" and regularly do heavy barbell squats, deadlifts and daily stretching. I mainly hill climb on both bikes, but ride differently on each bike. My gravel bike does seated trail climbs at low gear. With the shorter cranks it's nice just to control speed with high/low cadence. With my road bike which I use for paved road hill climbing, I stay in the big chainring and ride out of saddle, where the longer crank arms help with the extra torque. In this case I monitor my heart rate and know when I'm hitting my limit.
Honestly I think crank arms are more dependent on your ride style and the conditions you ride in. The body can adapt with proper training and conditioning.