I checked and couldn't find a way to make the stars smaller while in the game.  It's possible to use a mod to change the sizes to whatever is wanted.  Some of the stars are supposed to be dwarfs or giants, so this may break the idea of having different star sizes.

In version 1.05, a change was made to how the planet labels work.  They can be in the way when trying to see what is behind them.  The change makes them vanish when the cursor is put on them, then they reappear when the cursor is moved away.

Using this method to make the stars vanish could be a good solution to this problem.

Yeah at the start of every game i just set my cam to view top down. But also resolution and various particles/gfx quality settings change the map visibility dramatically, most likely because bugs. In more modest graphic settings I can no longer see black holes and the like, just the antimatter around them but it's still fine to navigate. At 200 turns + on the most dense map setting it gets pretty vomit inducing laggy (10fps, visibility chunky), so turning all the FX off is required.  The edge detection is way better than it was though, i can click on a miasma of icons and hit the one i want now at least, so the UI is much more polished/practical than it was previously. Max 4k UI size is broken because the upscale of the resource icons pushes everything off the UI list requiring you to constantly paddle back and forth which you end up just not doing and then running out of things all the time, which is absurd, having a 43" 4k screen and you can't find a way to fit 20 icons on it? Strongly recommend revisiting your core style guides and where creativity can't solve it maybe just use rollover resource container popouts, there's at least a dozen ways to contain this info in a way that doesn't massively suck. But dropping to next level of UI scale down and they fit fine, and with new glasses I can see all the things just fine

If you hover over the planet labels, they temporarily disappear.