Former lawyer here, though this isn't legal advice etc. This is really more of a commercial question. Launching first puts you at risk of taking on personal liability, but most very early-stage founders are comfortable with this because they have 0 or negligible users.

On the other hand, there's a lot of value to launching quickly, and IMO usually this benefit outweighs the risk of personal liability. I'd just try to make sure that your terms of service includes a limitation of liability / indemnity clause.

One underrated aspect of not incorporating is that it keeps your company feeling more like a "project" than a company. And I think it's worthwhile staying in this stage for as long as possible, because it gives you more permission to experiment with wild ideas and iterate in weird directions, even if, as in your case, you have a pretty solid idea of where you want to start already.

FWIW, I didn't bother incorporating my own startup until I'd secured terms for my first fundraising round.

The YC advice I have read tends to be launch.

The best favor you can do for yourself is get to "no" quickly.

Then you can decide what to do about it.