How to use burst / slow-mo features on Nexus 6p?
This is for Google Camera v3.0 and up:
Video

Open Google Camera app
Swipe from right to left for Video mode.
In the top right, touch the icons to turn features on or off:
Slow motion: Set slow motion to 120 fps or turn off slow motion.
Note: On Nexus 6P devices, there's an option for 240 fps. 240 fps produces a higher quality slow motion video than 120 fps, but requires more storage space on your device.
Flash: Turn flash on or off, or set to auto (for auto, you'll see an &quot;A&quot; in the icon).

Photo

You can choose what Google Camera does with your photo bursts. There are two settings you can turn on or off:
“SmartBurst”: Automatically save only the best photos in a burst.
“Auto-generate creations”: Automatically turn your photo burst into an animation or collage.
To turn these settings on or off:
Open Google Camera app.
At the top left, touch Menu  &gt; Settings &gt; Burst settings.
Next to each setting, touch the switch to turn the it on or off.

For full details see:
See: https://support.google.com/googlecamera/#6306661