Indeed great conversation. I´m no expert at all, just trying different things with different tools and judging what my ears tell me.
Back to the FX, i really experienced that if i choose to use FX it works much much better and it sounds more detailed still with several layers if i put my FX as insert per instance and not sending all synths trough the same send f.e.
If i send huge sounds trough the same reverb and/or delay instance it gets really fast very muddy and washy. So polyphony also at FX, distortion, saturation etc. is (at least for me) mostly the way to get a huge but still kind of pronounced and not to washy/muddy layer. But like i said i´m no expert and it might be nonsense from other people view.