My team isn't full — can we still play?

Yes. A team that is not full when registration closes still competes, with the roster it has. Nothing disbands it and nothing removes it from the bracket for being short.

You will be at a disadvantage if the format expects more players, so it is worth recruiting while you can — share your team name so people can find it in the Teams tab. But an incomplete team is a real entry, not a provisional one.