I can see differences, but in order to understand where they are coming from I would need to be able to run this project on my end, change settings, CVars etc. So if you can send a repro or show this based on available UE content then I could dig in and figure out what’s wrong here. If this is only screenshots, then I can only speculate what causes those differences.
With roughness [0-0.05] denoiser is completely disabled, so they should be 100% sharp.
As for the moving blobs, I guess that’s GI in reflections. RT Reflections used static lighting (lightmaps/reflection captures + unshadowed skylight) for hits in reflections. If you want the same, then you can disable LumenGI and maybe will need also to enable r.Lumen.HardwareRayTracing.HitLighting.ReflectionCaptures 1 if you use those in your content.
In any case, with relying on baked lighting/unshadowed skylight reflected scene should look 1:1 the same between Lumen Reflections and RT Reflections.
What do you exactly mean by “Lumen shadows”?
Lumen is handling only indirect lighting. If this is about ray traced shadows and VSM, then it’s outside of Lumen and I don’t think anything changed there.
If this is about shadows in reflections, then that should work the same, we just have a different default and now all lights in reflections cast hard shadows. UE5-Main/5.5 got a new CVar to change that (r.Lumen.HardwareRayTracing.HitLighting.ShadowMode) and we’re thinking about exposing it in the PPV.