Hey there Matt, welcome to the forums!
What platform do you wish to have your game on? If you want it for HTML5 on computers (NOT mobile), then I personally find that the performance of Construct 2 is VERY good. I have many effects going on in my game to make it look great and feel atmospheric, and the game runs smooth as butter. Old computers that lack decent graphics cards will usually run poorly, but that's to be expected, since they have bad graphics cards :P.
Check this out, it's a comparison from the original "Construct Classic" and Construct 2 (That used DirectX rather than HTML5, so logically it should have better performance results than Construct 2, but Construct 2 is better in the tests):
scirra.com/blog/102/html5-games-faster-than-native
IF you want to aim for mobile, you may have a bit more of a hard time keeping the performance to a brilliant level if you want to have a high amount of detail and effects.
There's a blog post from Scirra explaining stuff mobile-related here:
scirra.com/blog/112/remember-not-to-waste-your-memory
The concept of having tiles, then decorating the tiles with more objects to make everything look unique is common practise, and in the above link to the blog post, it is explained that the game Rayman Origins uses this method, which is interesting to know :P
For sparks and debris and stuff, there's a built-in Particle object that is very simple to use, or you can happily make your own particle system with events :P
Hope I helped in some way!