I am very new to video editing and trying to learn, so please excuse me if this is an obvious question.

I have a video on a time-line, shrank it down using PiP, applied a circle mask, and parked it in the lower left corner, so it's like a talking head of me. I use the rest of the screen to display information, images, etc.

At some points I would like to enlarge the image of me to be full sceen size, and remove the mask. Then move it back to the corner for the next section.

Can I do this with keyframes and PiP and just leave the video alone (mpg) inside of that? Like working with an object, resizing and moving it, but doing that with a video? Do I need to set keyframes?

Or should I slice and dice the video, adding the desired effects as I go? And if I take that route, how do I add effects, like transitioning between the different settings, ie talking head to full screen and back again?

Thanks for any advice on the best way to approach this. Making tutorial videos, so most of the time I want to use the talking head in the corner.