The following formats are currently supported: mkv, avi, mp4, wmv and nut (And only WebM for Wayland's GNOME session). You can stop the recording process easily by right-clicking the icon and choosing "Stop Record". Or middle-clicking the recording icon in the notifications area (but doesn't work on all interfaces).
Green recorder uses the default audio device you have to record. So if you want to change the audio input source, you just need to change it from the system-side (using pavucontrol for example).
By default, On Wayland only, Green Recorder uses the V8 encoder instead of the default V9 encoder in GNOME Shell because of the CPU & RAM consumption issue with V9. Which -- now -- should also give you better performance. On Xorg, each format uses its own default encoder.
Install Green Recorder on Ubuntu 16.10/16.04
Open the terminal and run the following commands
sudo add-apt-repository ppa:mhsabbagh/greenproject
sudo apt update
sudo apt install green-recorder