I have 2 questions here. One, can I use a USB web cam for something like Google Hangouts. Two, can I install the Google hangouts plug-in on Raspbian.
I used my raspberryPI3B+ for google hangouts yesterday, with a cheap logitech usb webcam, and it worked pretty well. As a google account holder (gmail, google-drive etc) I did not require any plugins. Using the chromium-browser (on raspbian-stretch) I opened up my gmail account and clicked on hangouts option, whilst the camera did get recognised, I needed to change the audio from default (whatever that is) to use the builtin camera microphone (same usb address as camera). The callee (Norway) was using an android phone (with a hangouts plugin), so I just made sure I was setup listening (UK) when he called.
Yes you can Google hangouts on rpi with Chromium installed.