One of the cool things you can do in Construct is add multiple effects to an object. For example you can add a Warp effect to distort the object, and then apply...
Mobile hardware is sometimes weaker than desktop systems. One of their relative weaknesses is they can process effects with lower precision than desktop systems, which can make some complex effects look worse.
Could the WebGL effects be throttled somehow? Because when I was testing on an IPad Pro and Google Pixel phone (Good mobile hardware) the rest of the game/fading behaviour/moving sprites/animations were running silk smooth.