Using a webcam:
The webcam is very useful for vision and is more flexible to move around the robot than the phone.
There are several issues with this though:
You need to make sure it is plugged in very tight to the connecting usb hub otherwise there will be an error.
The webcam uses a lot of energy and processing power on the phone and expansion hub.
This causes disconnects randomly.
The webcam uses too much electricity and causes the robot to crash. The solution is just to get a special Anker hub that can be powered with a power bank. This is legal to have a power bank under the FTC new rules.
Also the processing power issue is solved by disabling vision as soon as it is no longer needed.
We used the Logitech C930.
Hope this was helpful!