That's an in built feature on Android OS called digital wellbeing.
Yeah I have a pc but it's low end so I just use it for casual use and storage. The real work is done on the tab and I just use my phone as an extra screen to look at references while drawing.
Personally I think it's better to use a tab than a PC because the backpain will be super high since I spend hours to complete a drawing plus it's mobile.