On most laptops with both Nvidia and Intel graphics they use Optimus for graphics sharing.
When Nvidia is selected, this will first process everything on the Nvidia GPU then send it to the Intel graphics before being displayed.
This adds some latency which can be seen by the 20ms render time.

The Nvidia card has more GPU processing power, so you should be able to do things like complicated chroma key virtual sets ec
without the render time rising too much, whereas if you used just the Intel graphics, the render time may start small but will quickly
jump up if using a lot of complicated inputs.

Hope that helps.

Regards,

Martin
vMix