I think most of them are incorporated in California. It remains to be seen whether the company will relocate to Cayman Island.
US withholding tax is dependent on the tax treaty the US has with the country where you live. You can look it up. 30% should be standard. For me in The Netherlands it is 15% because we also have a wealth tax and it wouldn't be right to charge us twice.
Both verticals are US incorporated and we will be seeking W9 Form from shareholders that will determine whether dividends will have tax withholding or gross gets paid...