So if anyone is interested:
HoloMyth Debut Teaser video: 349K views
LazuLight Debut Teaser video: 1.3m views
HoloMyth Country Roads collab song: 456K views after 2 days.
LazuLight DCL collab song: 347K views after 1 day.
Hololive English official channel - 123K subs
Nijisanji English official channel - 109K subs (up from 97K post-EN debut)
You can say what you want about their meme humour, but they've been a hit so far. As an aside, NijiID's latest batch average only half of NijiEN's current subscriber count, and given the fact that they've just opened auditions for Gen 6, it's abundantly clear that Nijisanji have grounded expectations of their branches.
As soon as the clippers start having more material with which to promote LazuLight, they'll continue to grow. Holo clippers have already taken a shine to them, so there will be a big overlap in fan bases down the line.