If I understand correctly I think you are confusing legal structures with the business side. Apart from the equity split, your business model can change 100 times and it won’t affect your legal structure. The legal structure will affect in the easiness of fundraising, or applying for grants but it in the business model or titles themselves.
If it will be in the tech industry you should get a C-Corp for future posible fundraising. Apart from that the other questions are not tied to the legal structure.
At least from a business perspective.