KB10809 - How to render street map line intersections so that the outlines (at the line edges) intersect nicely for best visual presentation?

The solution is to draw the street map line layer twice, i.e., have the same layer two times in the project, one layer on top of the other layer. First draw the full width lines representing each road or street in the lower layer. Then render the same lines a different color and more narrowly in the upper layer, so that each narrow-rendered line in the top layer partially hides the wider version of the same line in the layer below. When the two layers are viewed together, the result is that the upper layer forms the line interiors while the still visible edge portions of the wider lines in the layer below form the line outlines.

The alternative, of course, is to just use the line outline feature within the visual layer property control. This works great when just quickly setting up a project, but the two-layer method described above will deliver the nicer visual result that you would like to achieve.