I do not have a good recommendation for the thick outlines besides what you are already doing.
About the wall-fascia lines: if the fascia line is showing on one elevation and not showing on the other, I would suspect some minute modeling inaccuracy that is causing those lines not to disappear like they do in other elevations. I would zoom in very very close and check whether that is the case or not.
Another thing I can think of if there is no way you can make it disappear is to model the fascias using the Morph Tool, then select those edges of the Morph Tool and make them hidden. Hopefully then they will not be shown on the Sketch Rendering either.
A third option is to just draw a white fill over that line. In the past this is something I have always been doing because I always tried to keep all my Viewpoints in automatic update state and covering the unneeded lines with white fills was a solution I could live with.
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