Line styles are dependent on the ‘Cosmetic’ and ‘EndCap’ settings. For Cosmetic pens with 1-pixel wide lines the dots are elongated. For wider lines it is possible to get round dots by using the ‘pecRound’ cap style.
If you want to get 1 pixel dots followed by 1 pixel spaces then this works for dotted Geometric (Cosmetic = false) pen but only looks OK for horizontal and vertical lines. Guess this is good for grid cell borders.