I'm wondering how many motors I can control at the same time using the LEGO Powered Up system? What components are required to make this work?
With current hardware, the answer is 10. From the trains FAQ:
You can run up to 10 trains at the same time from one remote control. There are 5 channels on the remote control (you can tell them apart by their different colors), and with each channel you can control 2 Smarthubs in separate trains with motors plugged in – as long as on one train the motor is in port A of the Smarthub, and on the other train, port B.
Each Smarthub provides two ports:
There are 5 channels available on current remotes, so you can pair up to 5 remotes with Smarthubs and control 5×2=10 outputs at the same time.