Nothing you said is a red flag. Introverts work with extroverts all the time.

Co-founder relationships are like marriage times two. You spend all day together, you’re financially bound, you will disagree and you will need to resolve conflicts. You need to measure that.

Deliberately bring up the thing you disagree about most. Work together till one convinces the other. If that process leaves a bad taste in your mouth, break up early. If you can’t do that with anyone, you need some emotional intelligence before you found a company.

I had a co-founder who I really liked. We had a disagreement where I was seeking a fair outcome. He threatened to kill me and left the call. This is an extreme case but it illustrates the need to measure conflict resolution.