breather or oil cap?

Hi Everyone!
I have Mopar valve covers that only have one opening per side. Knowing that I’m running a PCV valve on one side, should I use a breather for the other side (doubling as my oil filler) or should I use a closed off oil cap?
I seem to be getting some oil blowback coming from the breather I am currently using.
Thanks for the help!
View attachment 1716038212
A pcv on one side and some kind of breather cap on the other. The breathers usually double as a oil fill cap.