What do you ask a founder to work with to verify they're competent?
I'm in a position of potentially going to be first engineer and am really not sure what to ask and gauge whether going from a cushy job to a risky startup is worth it? They have customers, but not many, as well as a very high conversion rate.
They also have some a small amount of pre seed.
I dont have to ask anything, the interview process normally speaks for itself. If they have the emotional intelligence to have a mature discussion about their company, product, and after questions to you, they sell themselves as a potential employer, it's a good sign. If it's mostly inane gotcha questions followed by an email to do 3 hours of leetcode monkey tricks, I've seen all I need to see about the how they view the quality of leadership.
What do you mean by competent, and what are you looking to get out of the job?
Once you define those, you should be better positioned to determine if the company and the founder are a good fit for you.