Separate issues. both related to TAA.
The wall is shadoewed. The shadows suffer from the engine’s incapibility to render.
Really, sort of similar with the rocks.
The difference is that because this is a TAA issue, even if you bake the light you will still get a very similar result.
Really all you can do if its this bad is change away from TAA.
FXAA? MSAA?
see how much that changes - and make sure that your scalability settings are all set to epic too.
Ps: 90fps is very low. You are in pie and not in fullscreen. That aside, i dount the video you shared was in 90fps since you can see the frames skipping (and yes, what you shared is recorded at a different frame rate than what you see, but the effect on the floor is what gives away the lower fps).