Pixels brushes

Hi everyone, I'm new to fresco, and one thing I can't understand is, when I use pixel brushes, and I need to zoom the drawing for the details like face, eyes, hands, hair etc.. It has a "pixeled" texture that really bothers me,, I was wondering if it's my device, or it's just designed to draw "big" or "less detailed" illustrations (if it makes sense). 

It doesn't happen with vector ones, I use pixel brushes cause there is the mixing brushes pack, if vector brushes also have a mixing pack please send it to me so I can use those instead.

Thank you y'all in advance🫶🏻