I left in February of 2021, but at the time it was competent but unexceptional. Rival Wings and Conquest(?) were the two big battle types, and I think overall Rival Wings was more interesting, while Conquest usually devolved to a round robin rotation of objectives or endless stalemates unless you had a competent caller directing your nation’s team. I didn’t like it at all, but Rival Wings was always dead outside of events. Rival Wings was like a “MOBA mode” plus vehicles, so a big thing was objective and resource management so you could push an organised vehicle fleet down one of the lanes. Engagements were also typically smaller than in Conquest.
5v5s were very unbalanced but fun for casual play due to job variety, although the high end was being griefed by some notorious hackers around November of last year (which is when I lost touch with the PVP community on Twitter).
In terms of activity levels, I could basically always get a Conquest match or a 5v5 match, but I basically finished my 5v5 achievements and then only ever played Rival Wings when there were enough players to start a match. They’ve recently introduced a reward track for all PVP, so maybe Rival Wings has finally seen its Revival Wings.