I am using Skydemon on a Samsung Tab7 and a Huawei P9 as backup. [Both excellent]
Would it be possible to have a choice to make the width of the track line display narrower and the waypoints smaller?
I find them rather oversized in proportion to the map.

No, not really. Such fine customisation of individual details isn't something we tend to go for. If it's really necessary, it's because we got something wrong with the defaults. I believe town names are already drawn with a smaller font than everything else.