I've tried to play stems with lmms as a DJ set but when I put an effect on a stem and turn the effect down there would be all this awful background noise making it impossible for the stems to sound nice. My suggestion would be to add more effects specifically as DJ effects. Yes, I am aware there are already effects with DJ in their name but these still have this awful noise issue, there great for producing music but awful for djing.
There are many effects, so you have to be specific. What effect and what do you mean by "turn the effect down"?