thanks, the pic is very clear and easily digestible. it seems that plymouth-quit-wait.service takes the longest (~23s). if i understand correctly, plymouth is essentially just some boot animation. is it a good idea to remove/disable/skip it?
edit: curiosity got the better of me. after following the steps described here, i have managed to remove the fancy plymouth boot animation and went from 40-ish seconds to 20-ish. good enough for me. cheers!