Am I understanding it correctly that you releasing Hindu countries in peace deals to force-vassalise them to integrate them later? It’s seems pointless to me if your main concern is AE. If they are Hindu you should conquer them directly because as you notice - conquering Hindu cost little AE in comparison to Sunni in your case.
Of course using theirs Reconquest CB is good thing, but if you don’t use it then it’s not worth hassle.
I don’t like to integrate small vassals also because it cost dip rep every time you finish process. -3 dip rep is a lot especially when you want integrate another vassal in the same time. Feed them a bit before integrating. How much dip points you pay every month to integrate vassal? Who is your vassal btw?
Of course using theirs Reconquest CB is good thing, but if you don’t use it then it’s not worth hassle.
I don’t like to integrate small vassals also because it cost dip rep every time you finish process. -3 dip rep is a lot especially when you want integrate another vassal in the same time. Feed them a bit before integrating. How much dip points you pay every month to integrate vassal? Who is your vassal btw?