I used to be a newbie like you,so lemme help you out too :3 1.no,aerodynamics aren't in the game yet 2.RCS helps handling large ships,by thrusting little amounts of monopropellant. But probably the main reason they're still living is for DOCKING.They're unvaluable in docking. 3.Vectoring engines have gimbals,which help to move the end of the engine a little,which can help handling the rocket. 4.Currently,the probes aren't very useful now if you have any more questions,I would be happy to help. also,don't be afraid to ask,community is very friendly here!