You'll really enjoy small hive beetles if you get them. You'll spend a lot more time in the bee yard.
They're not much of a problem in a strong hive, but they'll take over a weak hive in no time. And if you make up nucs, you better make sure they're strong and in full sun.
I really don't worry about varroa too much, I have pretty hygienic bees and oxalic acid, if they need it. But I haven't found anything that really works against the beetles.
Now that I've gotten completely of track, I don't think the PVC entrances will cause any problems. I know a guy that has some pipe entrances and he doesn't seem to have any problems. I can't see how it would be much different than a drilled hole for an entrance.
I've got a couple of nucs with 3/4" holes and they don't seem to have any issues with that. I personally believe that ventilation is over rated. But that's a topic for another thread.