I will work with a coder. Should I give customer journey? Or user stories? Or user flows? What is the order?
Before even beginning to think about launching your project you need to evaluate why you want to do it at all. Just doing it "because" is going to make you go mad, you'll want a reason to do it because it will be taking much of your time up. Make sure you go over strengths and weaknesses . If you are just doing a random journey story here and there I wouldn't add it but if you are great at bringing in people with your stories then that would be great because it would help people be more intend with your project . Keep a calendar that you can keep your deadlines on so you don't forget because I have seen this many times as well .
Great that you have an idea you'd like to pursue.
I'm not completely clear on what stage you're at, but have you validated your idea with real people? Have you talked with individuals (outside of family and friends) to confirm that the problem your project resolves is something that potential customers are looking to solve? And they'll be willing to pay for it? And they'll be willing to switch from whatever they're doing to resolve it now?
If you wish to discuss, send me a PM through Clarity for 15 free minutes.
before starting the project, I highly recommend to read Michael Gerber's "E-myth revisited". It will help you to focus and to get clarity.