I don't see much of a difference between very high and ultra and in some cases no difference at all but I'm getting older and maybe my eyes just don't see as clearly as they used to.
cause there is no big difference.
here's what I proritize:
ambient occlusion-usually go highest possible cause it's one of,if not the most,important setting for a lot of games,the main factor contributing to the realistic look of objects and environments imo.
anti aliasing - super important for me to have detailed image with no jaggies,same as above,very important for the realistic look of environment
textures
level of detail - very important,though does not always need to be on ultra,after a certain point you get a huge performance hit for what does not increase the image quality where you'd see it anyway.
vegetation/terrain settings - usually go with max possible,though I will say that for vegetation: high/very high setting with higher antialiasing usually produces a better effect than max setting with some basic aa.that's why I mentioned aa as one of the main factors - the amount of objects it affects is too big to treat it as of secondary importance.
for terrain it's just important to have it cranked up to the max cause it's where you vision is focused.the more tesselation and detail the ground gets,the better.
here's what I think about other settings - like screen space reflections,shadows and volumetric effects.we got to the point where the devs are getting them to ridiculous levels.take ssr - at max lot of power is going to producing a sharper reflection,and while it costs a lot of power the effect is usually not that visible over just high/v.high or just having them on.such is the nature of reflections - they are in constant change.is there any point in making them super crisp if it costs you a lot performance? shadows - a lot of the times ultra shadows means they're just very crisp and accurate,to the point where it costs you a noticeable chunk of performance to produce a bit sharper and detailed shadow of a screen object that'd you only see in static image and you'd have to look well.volumetic effects are the most ridiculous of all,cause the performance hit for what you get in return ratio is the worst.
ssr at high,shadows at very high and volumetric effects just on - that's the best combination for me.you're getting a lot of your pefrormance back,and it's exactly where you won't notice much iq degradation if any.you're not actually missing anything,just making it a bit less accurate.the performance uplift may be huge at the same time.
It's definitely much,much more important to have more detailed objects and environment than their reflections and shadows,where you can absolutely make some sacrifices and not even notice them.