-20c to -40c is your target temp (ethanol wash) to lessen or even rid completely the lipids and waxes you often get when washing biomass (cbd, cbg, thc). This skips a step (winterization) when washing at those temps. Heat degrades terps. The terps get separated/fractional off when in the short path at certain temps and vacuum depth.
Heads - residual solvents, water, terpenes
Main - (body) distillate you want
Tails - end of run, low grade tcc %
You want sub 100 micron when doing a spd run. I like sub 25 micron for my runs. A harbor freight vacuum pump isn't gonna cut it. Alcatel 2021i, edwards 30, and a few others. For a rotovape a diaphragm pump is ideal. Or the faucet vacuum pump can work on a 2l rotovap.