Thanks a lot for the replies, guys!
I’m still a bit uncertain. From what I’ve gathered, ISM doesn’t support LODs and HISM doesn’t support per instance culling. This renders both options completely worthless to me, at least for this use case.
Is leaving everything to automatic batching (behind the scenes magic) all I can do?
And in the topic of the vertex painting, would you guys consider it a definite no no?