Because the scene painting view is a snapshot of the scene view, you can set its display resolution. With lower resolutions, you will see pixelated effects, but the strokes will render more quickly when you refresh the view.
To change the resolution of the scene painting view, select the desired resolution from the Paint Effects panel's Resolution menu. The final render is not affected by these settings.
Fits the view to the available space and displays it at maximum pixel size (no zoom).
Displays the view at the selected percentage of the full resolution, occupying the same the screen area by increasing the zoom level.
Displays the view at its actual pixel size (no zoom). You can also select this resolution with the 1:1 button on the toolbar.