Thanks, I didn´t know that thecnique, BUT… that’s exactly the problem I was mentioning, If you add a plane to the scene and play it from there, everything else in the scene affects the video quality, for instance, that video is affected by lighting and shadows, it also looks orange LOL.
For me, it would be easier to just use a widget, (haven’t tried yet, I confess, but it might keep my quality high) my video is 4K and it looks fantastic if I double click over it in my PC folder, but using a plane in UE, makes it look old, weird, poor quality and that’s exactly what is happening to the tutorial video after using a plane, perfect example of downgrade; a widget might keep the quality, not sure about different PC screen sizes honestly, like, for example if you use VLC to play a video, depending on the size of your screen it will add a black edge up and down, so the video will perfect match any screen size, not sure if the widget does that, but at least I won’t loose quality, still… I cant add it as a widget to the sequencer… 
so that I can perfect sync the movie with other effects, because I wanted to also make the sound effects with UE, for that video but I cannot visualize that video in the sequencer.
so weird, that a “cinematic” tool can’t incorporate pre-rendered movies, full screen and high quality right out of the box.