I play with headphones sometimes and speakers at other times.
Two questions:
Is there noise/echo cancelation or is playing with speakers and having my webcam's mic enabled going to annoy everyone?
Is there some way to make it so if my headphones are plugged in, that mic is used, but the webcam mic is never used? (Short of disconnecting my webcam ofc...)
You can pick and choose your input/outputs in the Voice Chat Settings menu. This should help with your second question too!