Don’t sweat it.
I’ve co-founded successful start-ups “both ways”.
The first time, it was pure white space we saw. We saw an opportunity others didn’t, put together the team, and went for it with 100% conviction. One idea. Period. Just one idea.
The second time, it was a team in search of an idea. We had the co-founders, we just weren’t 100% sure what we wanted to build. We wanted to do “Flickr for Your Docs” or something similar. We went through a bunch of ideas with the same team. We built a prototype of a totally different product, for a totally different market, and threw it away and started from scratch.
Generally, I prefer the first type of start-up. The founders are more mission-driven here, usually.
But both can work.
Keep it at. Kill all the ideas you don’t 100% believe in. There are more of them.