You are able to mix gamepads and smart phones! Though there is a limit that you can only connect a maximum of 4 gamepads to a single session due to limitations with the JS gamepad API.

Would you be interested in also beta-testing our upcoming 3rd party game development SDK? If so, please ping me on our Discord (link at the end of the gamingcouch.com web page) so I can take your contact details for the beta-testing list :)