Thanks Mark-Kashman for your suggestion. I have indeed considered that and will do so for a few Apps that will be used primarily on mobile. But it doesn't solve the problem that any user who installs the Lists app can kill my workflows by changing any column they want because everything I'm hiding in PowerApps forms is revealed in the Lists app (and in the SharePoint App as well btw). I just don't see where the problem is in displaying the custom forms. You're doing it in the PowerApps App on mobile and it does work in the mobile browser, so why not do the exact same thing in the Lists and SharePoint Apps?
Furthermore, creating a complete PowerApp is a nice thing,but why do the extra work when the Lists interface is already there and looks just fine?
Thomas