Hi, agree this is a nuanced area. I can comment generally on how other founders have threaded this needle. The IEP isn't a very mature or robust alternative at present.
As you know, the H-1B category is quite strict in permitting paid work only for the H-1B employer-petitioner. It prohibits paid freelancing of any kind, including driving an Uber, running a paid Substack, working for an overseas employer, and monetizing your side project. That's the bright line you start with.
So, Step 1, what can you do with your side project that keeps it in the realm of a hobby, while in H-1B status? Probably quite a lot. You can test and perfect how the thing runs. You can polish the user interface. You can talk to your target audience, every day. You can immerse yourself in how they describe the needs, hopes, fears, etc., that your product addresses. You can set up a special-interest website for it (but not on Shopify).
IOW do it for fun, not for money, at first. Take it as far as you can in the special-interest realm. Get all the "hobbyist" moving parts working together.
Step 2, start building your O-1 visa evidence portfolio, at the same time. Pick a niche, related either to your side project or your job, and become a subject-matter expert in that thing. Publish, do podcasts, get interviewed, do open-source, attract some "sustained acclaim." As long as you don't get paid, it's perfectly consistent with H-1B status to become an influencer in your niche specialty.
Step 3, when your product's ready to monetize, you'll also be ready to incorporate, have your company sponsor you for your O-1 visa, and have an O-1 evidence portfolio ready to go. Alternatively, present yourself and your product to an accelerator, O-1 portfolio in hand.
Check out the links in the "Swizec" comments above. Swizec didn't have an H-1B, as I recall, but he's absolutely cracked the code on how to build your own O-1. And with an O-1 portfolio already built, you'll have many, many options for moving forward.
Long answer to short question. But it's a great question! I hope this framing might help others who are tackling this challenge also.