There was 2 types of PVP WQ in legion. First, the towers. Both faction were asked to go to a different tower to kill npc, you had absolutely no reason to go to the other faction tower other then look for a fight, which you can do in any WQ. There are plenty of WQ that ask you to kill npc tag as the other faction in BFA. Second, the FFA pvp WQ, they had nothing to do with faction.
Now BFA invasions. 5 daily that give you 60 conquests if you do them with WM on. You know the enemy also have 5 WQ in the same area. And now for real pvp WQ, there is always up to 2 quest that ask you to kill enemy faction NPC, not while the 2 factions are on the opposite side of the maps, this time, while both faction are fighting in the same area. If this don't start pvp fights, there is always that one WQ that ask both faction to gather the same resource, and with faction tagging, you actually have a good reason to get rid of the other faction player.
So, in term of real npc, BFA incursion with WM on > Legion wannabe pvp WQ