Been doing some testing with multiverse. Took me about 5 mins to set it up. No fire bugs. Portal worked fine also no disappearing blocks ect on entry/exit. ps also compatible with world edit. Also when you step into a portal its faster than Pinapp. Multiverse has an addon that can scale the size of the nether so this could fix the nether issue.
I've used multiverse before and it caused issues (different ones to Pinapp and potentially less bad).
My main concern is about players having to use commands to set up portals. I'll check up on multiverse to see if this is an issue or not.