A video synth performance can be entertaining and inspiring. A video showing how to do something with a synth can be educational and useful. But anything purely trying to show how a synth sounds isn't really any of those things. The encoding just doesn't reflect the sound accurately, effects or not.

If you want to give an opinion about how a synth sounds, that can work. But you need to have enough content so I can get a sense of where you are coming from, what you tend to like and don't. There are a couple reviewers that I go to specifically for this reason.

And if you are getting something for free, or are being paid to make a video, be completely up front about it. Not that it means what you are saying can't be trusted, but it's part of the context I need to understand your point of view.