In terms of blurry models, I had a similar issue a while ago stemming from poor light map UVs. My solution was to let Unreal create the UVs automatically; I had to go back to Blender, and export the model with a new filename, then made sure the “generate Lightmap Uvs” box was ticked in the FBX import options. It’s easy to replace the meshes within the editor by right-clicking/replace with item in the content browser. After rebuilding light, the meshes with the automatically created lightmap UVs looked far superior, and in some cases I could use a lower lightmap resolution.
The flickering on the left side of your video looks like the Engine is trying to render two polygons in the same location. Make sure nothing is overlaping.
I had a lot of headaches with Raytracing running out of memory and crashing the editor. See if there are textures you can limit to a lower resolution. Remember – it’s running out of memory not only from textures used in your materials, but from all those 512 pixel lightmaps. I have also noticed that real-time raytracing creates a subtle “film grain” flicker, and I think we just have to get used to that with the current technology.