It's been a long time since I've had to tinker with settings to figure out how to get a game to run well, but barring some optimization, this is where we're at now. I spent most of Saturday messing around with graphics settings, and I've found several that disproportionately affect FPS. Reducing these settings has brought me from 15FPS on surface settlements and stations to a range of 40-60fps, on my Ryzen 7 2700k and RTX 2060 combo, in 1440p. Your results may vary
1) Model Draw Distance. I reduced this from the 100% default to 50%. This is the single biggest FPS vampire here. Basically it reduces the model complexity of farther away things, inserting lower detail models for far away objects. The farther to the right the slider is, the farther out the highest detail models are used.
2) Shadow Quality. Dropped from Ultra to High netted me a few FPS with no visible difference in quality up close. The difference between High and Ultra seems to be that Ultra renders shadows farther away. Medium offers a much larger drop, but you lose a lot of NPC shadowing at all ranges.
3) Field of View. A drop from the default, both in ship and in person, can result in FPS gains. I know a lot of people are sensitive to FOV, but it seems like even a few degrees results in measurable changes. I was able to go ham here, reducing it way down because I have a gigantic monitor and headtracking (And I'm used to Bethesda games with pathetic FOV) but I realize not all people can.
4) Terrain Work. This is an old Horizons tweak from back when it released and planetary framerates were miserable. Reduce it down to about the middle to help with planetary FPS if you're struggling there.
Other than ensuring that Supersampling stays at 1.0 or below (supersampling is directly related to the resolution being rendered, don't go below 1.0 unless you want your game to look much worse), the rest of the settings seem to have negligible to zero FPS impact and I was able to crank everything else up to High/Ultra with no ill effect. This results in a game that doesn't look very much worse than it does on Ultra, but runs an order of magnitude better. It's still not running NEARLY as well as it should for my hardware (I was at a locked 144fps most of the time in Horizons), but it's definitely playable now.
I think the reason it works is because of the culling issues raised in