Yeah, anyone who does serious Cycles rendering is doing themselves quite the disservice if they are not using E-Cycles. All gain, no pain. Though, some would say “pain of $99…”, but I say “yo fool, this thing paid for itself in one day for me!”…
I am not even using RTX (yet), but I do have three 980Ti Hybrids, and E-C is still crushing it for me. My renders pretty much cut in half, going with the settings I use most often. Speaking of which, the Quick Settings menu alone is worth the price of admission.
Here is the E-Cycles thread, which prolly has some of the highest traffic on blenderartists: