Nah, it is not. Rad video player doesn't load unreal engine, doesn't load shaders and 3d models. It just converts .bik and .bk video files from game files in real time. So switching grafic preferences you just swtich real time converted video resolution.

Video decoding is also a hard work for video card + unreal engine

This is pre-rendered video. All of them you can open with Rad video player from game files in any moment.