zero sized line adjustments

is it normal for lines made with V strokes or zero sized pencil lines and then be unable to edit those to make them thick?

That is correct.
The Stroke tool draws invisible lines only. You cannot add thickness to the line.

Good evening,

You can right-click on select strokes and select Convert > Convert Stroke to Pencil Line.

Strokes are not quite the same thing as pencil lines.

Hope this helps,

Marie-Eve