Operating system: Windows 8.1
Graphics card: Geforce 860m, Geforce 980
Broken: 2.80, 2019-03-10
Short description of error
Scene strips in the vse will play back very slowly. This seems to happen regardless of render engine, or scene preview type in the vse preview settings, tho some settings and engines do provide better performance than others, even the best combination is still terribly slow.
For example: an eevee scene with only a camera and no special effects enabled will play back at 1-2fps in the vse, but animation playback in the 3d viewport will of course be over 30fps.
Note that this is not the same as the slow playback/rendering due to the color transforms, this still happens when the color is set to 'Default' transform and 'None' look.
Exact steps for others to reproduce the error
Create a second Scene
Add that scene to the vse of the first scene
I have attached a simple .blend file where I have tried to make the playback as efficient as possible... still only get about 2fps.