Three or four completely different trips sharing one island.
This is a shape, not a schedule. Each day has two anchors and a lot of slack, because 3-day itineraries that book four things a day fall apart the first time lunch runs long. Move things around freely — the neighbourhoods are grouped so that walking between stops actually works.
Villas with a pool are the reason groups love Bali: splitting a four-bedroom villa costs less per head than hostels elsewhere. Decide the villa-versus-mobility trade-off early, because the nicest villas are the furthest from everything.