mirror material are very difficult to get in game
are you in Software raytracing or HW raytracing? Software raytracing use distance field mesh , they are blobbly, voxel type proxy of your SM
also this noise is based on lumen use low quality sampling behind the camera
If your project is for offline render go with pathtracing , it’s the only reflection quality accetable, but if your project is a game aim for 30FPS you can try HW raytracing too , still flickering in the mirorr material, increasing number of sampling and lumen cards help but it will still flickering and if you get rid of the flickering you will have poor performance.
if your target is 60 FPS you need to compromise your reflection quaility with the default SW raytracing