Yes, this is “surface level” styling as a theme. It targets Inkscape-specific widgets as much as possible, which improves things considerably. It does not change Inkscape beyond the styling level

If you could explain your panel issue in more detail (I don’t understand what you meant exactly) and if there isn’t already, it would be good to submit it as a issue to Inkscape directly

nice, feel free to give any feedback if you have any problems with it.

I made/maintain a UI-style from scratch for Inkscape, if anyone is interested. It addresses various UI issues

https://gitlab.com/sxwpb/ink-sx-ui