Back in 2007 I built myself a gaming PC with two brand new GTX 8800 cards (SLI, baby!) and nearly cooked/choked them to death in first week of operation. What I learned back then was that nVidia drivers did not create a proper fan curve that would ramp up with rising temperatures and that I needed a piece of 3rd party software named Afterburner to keep my system cooled.
It's been nearly 20 years and probably a dozen different graphic card models since then. I have just finished installing a render box for my wife with a 3090 in it. Installed the drivers. Installed the Afterburner. Tuned it.
Then it dawned on me: Is this still a necessary step? What would happen if I did not install Afterburner? Don't nVidia drivers control the fans properly?
Logic dictates it would be crazy for the official drivers not to keep the card cool, but I've been doing it one way for so long that I am too afraid to experiment (risking hardware damage?).
When you're afraid to let evidence lead you, next best thing is surely asking strangers on the internet - so here it goes: Is MSI Afterburner necessary? What would happen if I don't install it? Do YOU have it installed?
My experience with the last Nvidia GPU generations is the opposite, the fan curves are too conservative temp wise. Your card will get very loud trying to maintain a ~70C temp target. This of course changes with manufacturer and model.
With a 3090 I suggest an undervolt (even a modest one works miracles for the power hungry top tier cards). And after doing that, you can also dial in a slower fan curve.
While finding a good undervolt is time consuming (please do test, stress the heck out of it, with different apps/games), it was a god send to me. And it helps a lot with keeping the memory cool, which is something I worried a lot with the ram chips on the back of the board that the 3090 has.