Blender's Video Sequence Editor just has a couple of quirks to get past. It is not deeply mysterious. Like: the VSE viewer and the Image viewer are similar but

Blender's Video Sequence Editor just has a couple of quirks to get past. It is not deeply mysterious. Like: the VSE viewer and the Image viewer are similar but distinct; that can be confusing. And OpenGL acceleration on a Scene strip shows a 3D model rendition that is not (in general) the same as the rendered output of the Scene. If you want to get fancy with the compositor + VSE, again there are just a couple of quirks but the learning curve is merely steep, not long.