Wow, distributing titles seems like something you should not be worrying about! The CEO is responsible for, in a word, everything!
If you are like most startups, his primary goal will quickly move towards sales and marketing -- and if needed -- fundraising. None of the rest of the titles really matter. Rolls and needs will change as things progress.
Instead of worrying about rolls, just go with "co-founder" and get on with getting product-market fit. Nothing else really matters. I'd advise choosing a CEO as soon as possible to handle all the business details. You don't want to drop the ball on accounting, taxes, licenses, insurance, etc, etc. The CEO can keep that in order and lead the sales & marketing & fundraising.