As far as the oil drain back from the "catch can" into the oil pan. My canton has a 3/8npt plug in the right side pontoon. Right below my catch can.
Initially I considered a simple drain back tube. When I discovered that every time I ran the car, essentially I would get about an inch and a half of water in it, I thought that would not be a good idea.
If the water is the result of condensation it will not make any difference because it is coming from the oil galley anyway regardless of if you had a catch can or not. Besides it will evaporate with the high temp of the oil like it normally would if you didn't have a catch can. If the water is the result of something other what is normal given the heat cycle then that is different.
In my case, adding an oil drain back is a solution in search of a problem.
I think of my catch can as more of a skimmer then anything else and the fact that I have no oil in it is likely an indication that I have the siphoning under control or even solved.
Adding water to the oil pan is not a good idea and is likely a doomsday device for the bearings.
So if it isn't broken, don't fix it.
I think that the Off Highway booklet showing the Boss 302 valve covers with drain backs to the oil pan was the seduction/eye catcher here but those were attempts at solving a different issue.
I wouldn't be surprised if I eventually experience some indication of some oil in the intake under hard deceleration, but I haven't as of yet. Vacuum is at it's highest level at that point. So I probably am not running hard enough yet?
I personally prefer braking to using the transmission as a decellerant. I've killed more clutches with using the transmission to slow the car then anything else. "Brakes are cheaper then transmissions", Brock Yates once wrote.
If you have some oil in the intake unless you are causing a spark plug misfire/fouling situation or you are contaminating a cataleptic converter, exactly what harm is it doing?
A hard cooked oil build up on the top of the valves or that part of the valve stem isn't desirable but that seems to come from worn valve guides with lousy stem seals?