I've got a bunch of mods to recommend for PC players:
DLSS & XeSS Bridge: https://www.nexusmods.com/starfield/mods/196
This one replaces FSR with DLSS or XeSS for if you have an RTX or Intel card. It gave me a 5% performance boost right off the bat, without changing any settings, just because DLSS can run in hardware while FSR was having to run in software.
Neutral LUTs: https://www.nexusmods.com/starfield/mods/323
This one gets rid of the weird color grading a lot of the environments tend to have, massively improves the look of the game imo. As a side benefit, it makes the black of space actually look black, instead of navy blue. Though I do recommend using his suggested modification to increase star brightness back to vanilla levels (or higher, I cranked mine way up to 500, vanilla is 110, I would have gone higher but above 500 you start to get weird flashing artifacts).
Smooth UI: https://www.nexusmods.com/starfield/mods/270
This one replaces the UI elements that normally run at 30 fps (the ship reticle, some of the menus, etc) with versions that run at up to 120 fps instead. Really makes the experience feel smoother.
QoL ini tweaks: https://www.nexusmods.com/starfield/mods/381
Just a few nice Quality of Life tweaks you can make to the ini, pick and choose which ones you want.
Quick & Clean Main Menu: https://www.nexusmods.com/starfield/mods/418
This one skips all the intro stuff so you launch straight into the main menu, and also gets rid of some of the main menu clutter, like the Message of the Day. Just nice.
Value to Weight Ratio Sort: https://www.nexusmods.com/starfield/mods/476
Makes one of your inventory sort options the item's value-to-weight ratio, so you can figure out what's best to hang onto and what's best to dump when you get over encumbered.
And finally, last but definitely not least, I recommend using SpecialK for anyone with an HDR display. The game uses Windows Auto-HDR rather than native HDR, and it's fine, but SpecialK can inject HDR and does a better job.
Basic instructions for setting it up and download link: https://wiki.special-k.info/SpecialK/Global
Instructions for getting HDR working: https://wiki.special-k.info/en/HDR/Retrofit
The main stable version doesn't work with Starfield right now, you need to update it to the nightly one from the Discord. There are instructions on doing that in the first link.
Enjoy!