Here are some RT comparisons I took. On a 3070ti at 1440p, high rt dropped framerate down to 50, max rt dropped to 40, in the open world. Interiors and surprisingly Siofra River ran at 60fps with some slight stutters (probably shader compilation)
The RT is only RT shadows from the sun, and RT ambient occlusion. No GI and no reflections. It's not much of a difference because of how good the art direction is. Probably not worth the frame hit unless you are running at 1080p (which I ran max rt at a locked 60fps). There is no DLSS like essentially every game with RT, so its rendering it at full res, the RT scale setting only changes the sample count. I don't think there is a denoiser either, its relying entirely upon the TAA, which in Elden Ring is not very aggressive and has a small frame hold, it looks great, the best looking TAA I've seen, but using it as a denoiser leaves a lot to be desired. As a result, on lower RT settings it can look quite grainy.
All my screenshots are on the max settings, only the raytracing setting is changed between them. The shadows look great, but not really worth it unless you are playing at 1080p with a 3070, or at 1440p with a 40 series, at 4k its too much of a hit because its full resolution, so its 8x more expensive than 1080p.
Exterior direct lighting, no RT vs max RT
Exterior indirect lighting, no RT vs all RT settings
No RT
Max RT, very nice looking soft shadows
No RT
Max RT, would be nice to be able to only use just RTAO, since the RT sun shadows are more costly and are less impactful
No clue why they added it, probably a feature that's going to be in Armored Core that they backported, it will probably look better and hopefully run better in AC.
