There's a case temperature sensor top right.
Higher case temps cause throttling.
Apparently simply holding your hand in the right spot can reduce case temp and cpu gets more power allowance.
Yes, the Surface Pro 4 has thermal throttling... but not what you think • /r/Surface
That's the time it will look at to measure average power. So at 28 it will review the last 28 seconds and if average is over power limit it will throttle.
It's how responsive to change you want it.
EDIT: quote fail, but you get the idea
I asked this very question on the Microsoft Store and was told by Microsoft Team that:
"No, Surface Pro 2 is not compatible with the Surface Pro 4 Type Cover."
Buy Microsoft Surface Pro 4 Type Cover - Microsoft Store
EDIT: has anyone tried it?
Fairly sure it was the latest firmware.
I didn't install it (no issues I felt needed fixing) and still have the Intel options
Unsure on fix. Rolling back driver may help, but I haven't tried so can't say it's safe. Installing latest direct from Intel may help, but again I have not tried that