From my observation, I would say there's three main fan demographics in the EN VTuber world: the Holo Box, the Twitch Box, and the Everything Else Box.
Some Holo fans do branch out, but it's a "walled garden" kind of deal where there's rarely any reason to go out.
Twitch is self-explanatory, mostly the big indies + VShojo, or the 2-view grooming meta.
The Everything Else Box is your Nijis (pre-Dokibird debacle), Phase, Idol and small corpo, plus other indies, but are likely to tune in to Holo or at least know what's going on elsewhere from osmosis.
So it's not a complete Venn diagram overlap, but it's the sort of thing where the average Pippa watcher knows who Watame is when she talks about her on stream.