My current modem/router isn't strong enough to power my exterior Blink security cameras and I'd like WiFi in my front and backyard. Although my home is pretty small (1500 sq ft) it has lots of brick interior and exterior walls so the signal doesn't travel well.

1- Does Google WiFi mesh work as an extension of my existing router? Or will it only utilize the modem?
2- I have an airstream in my backyard that I use as a guest home that is about 50 ft away from the home and I'd like it to have strong internet. Is it likely that one of the Google WiFi units would connect if inside the airstream?

Thanks, I'm trying to get this all set up before I go out of town on Friday as my wife and kids will still be home.