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It might not be as flexible or good, but I use draw.io to "draw" diagrams on screen during live streams or even pre-recorded videos.

> low cost touch enabled tablet

This has different context depending on what you mean... is it a drawing tablet or some sort of Android tablet?

Anything that help me to draw figures and write equations on screen

Okay, that's a drawing tablet... monoprice some basic ones I've used in the past (in the $60 range), but you can find some SEO spam articles like these (https://tabletunderbudget.com/best-drawing-tablets/) with better recommendations

If you're on a Mac, you can connect an iPad and record its screen (over the lightning cable) from Quicktime