What are considered best practices for a German/EU citizen to start a startup in the US? What would be the process to found a company and to move to the US to work for your own company be like? Or would it be better to found it Germany and move it to the US at a later point (after PMF for example)?
There are multiple options to working for your own company in the U.S. The most common paths are the O-1, the L-1, and the E-2 and E-1 visa. Creating a company in Germany first might open up a path to an L-1 visa but that's the only relative advantage to opening a company in Germany first. The E-1 and the E-2 require that the U.S. company be at last 50% German owned and that there be a substantial investment of German money into the U.S. company or substantial trade between the U.S. and Germany via the U.S. company. The O-1 is based your own personal achievements. If you can have German invested into the U.S. company (whether from you or others or both), which generally means at last $100k, then the E-2 is a very good and easy option and relative to the O-1, allows spouses to work.
Does this mean that if a German citizen registers a company in US and owns 100% of it and also invests $100k into it, he can get an E-2?