Afaik the CCV pulses somewhat, but is mainly pressurised (blow-by) especially under boost.
The inlet pipe is always under vacuum, assuming your BOV is working.
The inlet mani has vacuum under idle, cruise and engine braking.
It's pressurised obviously under boost...
The heads are either under vacuum during idle etc or pressure during boost. Dependent somewhat on how well the valves are sealing...
The heads are either scavenged or or fed air from the inlet pipe under boost or vacuum respectively.
The head breathers and balance pipe are crucial in assisting oil to drain back to the sump after eg extended high g cornering. Ideally each head having its own AOS located on the opposite side of the engine bay.
The role of the PCV is to scavenge the CCV to the inlet mani when the inlet mani is in vacuum, under boost the PCV closes and the inlet pipe scavenges the CCV via the 3 way connector between the CCV, PCV and inlet pipe.
Therefore the most appropriate location to plumb in AOS's are after the CCV and another between the heads breather inlet pipe return
Dual AOS's with seperate drains with taps allow for easy dianosis of major engine issues eg if you're loosing oil via the CCV (rings), heads (valves, valve seals) or both.
Some say oil cap AOS's are not recommended for extreme track use or extended high g cornering. Ymmv...
Meaning they're good for 99.9% of people 99.9% of the time
However any AOS anywhere in the system is a good thing
The key being to keep oil out of the inlet pipe and inlet mani...