Open Broadcaster Software: cross-platform streaming and recording program
Slides: Google Slides with Speaker notes
When recording: on one side of the screen I look at the speaker notes, the other side contains the OBS GUI.
Otherwise pop-ups or drop-down boxes of selects input fields are not visible.
Round cutout mask for OBS: https://www.versluis.com/2019/01/obs-round-cutout-mask/
I record each slide on its own with this naming schema: 010-first.mkv, 020-second.mkv, .... This way I can insert videos later.
Before recording: If you don't need the mouse cursor to present something, then move the mouse cursor out of the screen, so it is not visible.
Since OBS worked very well I donated some money to them: https://obsproject.com/de/contribute
https://trac.ffmpeg.org/wiki/Concatenate
If you record yourself, then fairy lights with a warm white behind the camera give you a shadowless light on your face.
WebM is the best choice at the moment. See Can I use: WebM