Each multi-tenant strategy has pros and cons. Targeting large scale multi-tenant use cases might mean having a small number of tenants that are very large, or a large number of tenants that are very small, or anything in-between. My recommendation is to consider growth over time. It’s difficult to assess but things like customer onboarding, operational overhead, and cost per customer are all important considerations.
Imagine having a collection per tenant. Onboarding customers becomes cumbersome because collections and indexes must be created appropriately and (ideally) automated. Any changes to indexes would need application to every existing collection per tenant. And there are more considerations. But the additional overhead doesn’t matter much for a small number of tenants.
Most organizations want a single collection where sharding can provide scale. I don’t know if that applies here, but most customers succeed with this approach.
I hope this helps!