Nostr.land will limit it to a thousand or so, and a total of ~10K combinations per filter. Rate limits are dynamic based on the complexity of your queries and your AUTH status.
I would encourage you to split queries (at least for NFDB relays) in cases that aren't feeds, for example 1 per profile request. Internally it executes similarly but one means you won't lose an entire request due to rate-limits if they happen + the query execution can be parallelized more.