Depends on how environmentally unfriendly you want to be (tongue in cheek)
When your intake vacuum is high (idle and coasting) that tube allows filtered air to be sucked thru the engine (and thru the pcv valve) which removes moisture and therefore rusting/oil sludging from inside the engine
When the vacuum is low and crankcase pressure is high (full throttle) the pressure is relieved thru that hose into the air filter so as not to blow oil out your seals.
Plugging it off is a bad idea. Stuffing the hose into some kind of filtering device so the engine can draw clean air is better. The only annoyance with that hose being plugged into your air cleaner housing is the oily mess it makes inside!
You can buy a little air filter that replaces your oil fill cap and then you don't need the hose at all, but.... those lil filters will get pretty oily themselves and can fog/dribble all over the engine compartment. Gets messy.
Back in the my olden days, draft tubes were the thing. No smog stuff. Just a metal pipe directing that oil fog down under the car
Chose your poison, I guess. Just whatever you decide DON'T block your engine vents off completely. It's gotta breathe
