I feel like the setting item names should be left margined; they look inconsistent centred the way that they are. I also feel that the silver knob toggles are out of place and could do with being a dark matte surface. Other than that it looks exquisite. Well done!
Isn't the border on the record area a little thick? I know that it has to be used as a resizing handle, but the grab area could be wider than the physical border or grab handles could appear on hover. Other than that it is pretty sweet, although picture in picute could use a little more configuration (maybe a second smaller area that is dragged on top?)
"Picture in picture" is an option that displays the image from your webcam into the area that gets recorded - so that people can see you talk while you're demonstrating something. It would make sense to be able to configure it's placement and size.
May I ask where do you select the whole desktop/section option? I imagine it's the symbolic button next to the Capture Display, but that suggest me that if you want to record the whole desktop you have to manually select the area.
Whilst I agree with the recording-red button metaphor, it feels wrong to me, as red uses to represent an alert warning.
BTW, I love the Saving section, I find very interesting spliting the save directory and the save name; it feels very natural and logical. I would love to see that implemented in other applications, such as Inkscape.
Red is also the color for recording something as it yields control to functionality that deals with the currently recorded material. As long as you are recording, you cannot use a lot of the other functionality (like playing content) So the button color and the corresponding border color makes sense in my opinion.