I've run them open with nothing attached, I've attached hoses to pan evac, I've run hoses down to the frame somewhere like road draft, and I've also not used any breathers and just ran hoses to a breather tank.

They all work but the breather tank approach makes an oil change a little slower (have to pull the distributor to dump oil in quickly since there's nowhere else to fill it).

Pan evac is ok, I got 1" vacuum even with mufflers, tested with a gauge.
However I didn't like the proximity to my oxygen sensor so i got rid of that and currently have them open again. Also decided I didn't like the appearance of the hoses. Full circle....

pcv on one side, breather on the other will reduce oil contamination on a true all weather street app (mine isn't anymore).