I installed Safari 17 on Ventura 13.6 on my otherwise tolerable 2017 13 inch MBP w/o Touch Bar. It does seem more tolerable than previous Safari versions, but not quite as good as Safari 13 was on Catalina and not as good as the current Firefox is using the settings I mentioned previously. Still, I'm happy to see the improvement.
This MBP can't run Sonoma so I can't test it with that. I did use it for a bit at the Apple Store on a Mac mini with Apple studio display and an iMac both running Sonoma and it was pretty good also. The only thing I did to improve comfort on those machines was to disable True Tone. It seemed to cause eye strain on all of the laptops running the same version of Mac OS, even with True Tone disabled - not sure why. I've had a hard time tolerating any of the ARM based Apple laptop screens, but the desktops are ok for me weirdly.