If you're asking, here's what I would do. I would build the business case for the app. Sure, make a demo. Get feedback. Push it until it's clear there's a strong demand for the product, rather than an assumption that people would want it.

A good CTO is more than knowing Swift and if you ever have a technical startup, you're simply going to have to have a good CTO who is deeply technical. It's just a must. But you can honestly get most of the way there just by validating the concept so well that potential co-founders will feel like a fool not to sign on.

Also, you don't need great chemistry with a co-founder -- just mutual respect and open communication.

This is a really well phrased response, kudos to David.

My 2cents: Certainly have your hands involved in the product, prioritize the hell out of it; give credit to the fact that in order for this to succeed you will need to not be the CTO, unless that's the route you want to go, at which you should spend some of those 300-1000 hours finding a good business co-founder.