I use slides.com for lecturing in engineering classes and I often want to add explanations of mathematical content as I am lecturing. Currently the in-presentation annotation settings create thick and simple strokes that are not adequate for capturing written words or math. I think this would work fine if you reduce the thickness of the line, allow more control points (not sure if that is exactly the right word), and/or reduce the automatic simplification of the shape (also not sure if that is exactly the right word).

The default settings of the xournalpp app are excellent for this if you can imitate those.