I am the first “technical” hire of a startup. I think my contribution to both business capabilities and building the product is significant, maybe as much as a co-founder, but I would never call myself a founder. I founded an other company in the past that I kept running for 9 years, and I can tell the emotional and caring is very different regardless your impact and effort, even if it is 24/7. It is feel like being a stepfather. Maybe the best one, behaving and treated like a real one, but still…
I remember a beautiful family vacation that went wrong because as a solo founder everything that happened got routed to me.
If you decide to go solo, you will start hiring very soon just to make stuff happening before you run out of bandwidth.
And you'll need really high quality hires... wich need a lot of bandwidth to acquire so plan accordingly (if you can ;-).