I dry hop in bags in the keg and have not had any clarity issues. I leave em for the duration of the keg and don't weight them in any way. I dry hop out of the kegerator for 3-7 days depending and then put it into the keg to carb. I hadn't thought about purging O2 because I typically seal it up with CO2 and purge it a couple times, but then don't touch the prv again. I usually grab a batch of 10 when I hit up the LHBS just to keep some on hand. I typically dump the first pour out of a keg, then they run clear.