Later SU's had a breather connection between the needle and butterfly. This
ran at slight vacuum so scavenged the crankcase fumes as well as helping
reduce oil leaks (always an advantage on a Mini).
Prior to that, the PCV was the best bet as it did the same thing but
connected directly into the inlet manifold. Don't connect the crankcase
directly to the inlet manifold. I did this once. The intermittent cloud of
exhaust smoke when the engine swallowed a lump of oil was something to see!
Following traffic was bought to a stop.
The other advantage of running a slight vac in the crankcase is a slight
power increase due to lower windage losses within the engine.
I have never quite seen the advantages of crankcase filters as the gas flow
is out of the engine, not into it. There are some engines that run positive
crankcase breathing and still have an air inlet bleed. That's when they are
useful.
Early engines simply had open breather pipes. This can be used but the
resultant oily fumes tend to smell and make a mess of the engine bay. The
later types had oil separators. basically cans full of wire mesh that
trapped the oil and let it drain back into the sump. I would treat this spec
as a minimum for road cars.
Catch tanks came from a motor sport requirement so that blown engines didn't
dump their oil on the course. They can be used on the road but (assuming you
don't lunch your engine) are of little use beyond performing the oil
separation bit.

John