How to decrease brush lag?

When I try to use the brush tool on a layer that has lowered opacity, there is a significant lag with the brush strokes. If I use the pencil tool however, the marks show up immediately on the adjusted layer. Is there a way to reduce brush lag? Even on a normal layer, if I try to make too long of a mark with the brush tool, there will be a delay. If I do small quick marks, no lag. Any advice? I’m running a MacBook Pro 2015. Do I need a stronger computer?