I bet I could get away with not running fans at all until it hits 40c, then slowly increasing it as it gets hotter. CPU runs a bit warmer, about 10c higher than GPU on average, but even in my most intense games it doesn't get higher than 55c max.
Most default fan curves on GPU won't start running the fan until it hits 60c, mine don't start until around there. I haven't changed mine at all so it uses a zero fan mode until there and then starts. I don't know what speed it starts at exactly.
I may install afterburner at some stage and look at it. The GPU fans aren't on enough to be annoying to me. They stop running once GPU goes below 50c and most days it idles between 35 and 40c. (and that is in summer, winter will be fun). Mine don't need to run outside of games as I have those 2 fans under GPU doing their job for them.
Do you run the case fans at similar speeds. the GPU/CPU fans can only do so much if they aren't getting cool air.
if the case fans are providing the air, perhaps you can change curves on the gpu. It doesn't need to be a straight line from 0 to 100. None of mine are.
CPU for example
The CPU Cooler is hybrid, its got a 120 and 140 in it, so its speed is an average
How fast they increase can depend on size of the fan, my 140mm case fans don't need to increase as fast as CPU one does. to push out more air (that and there are 3 of them) and above some speeds I start to hear them.
Case fan curve:
The two 120mm fans under the CPU are running the fastest in case... but have the most relaxed curve
All 3 linked to the CPU sensor since its normally the warmest thing. Software can't see the GPU itself so its next best thing.
Looking at them all here on one screen I realise they all have a minimum speed until just over 40c and then start to creep up, all maxing out at 90c. The app doesn't show them all on one screen. How aggressive the curve is depends on what fans are attached to. CPU more important than intake for most part.
I was messing with them last night but in summer I can't tell if any fan noise I hear is from my PC and not actually from other fans in house cooling rooms. Wrong time of year to tell.
note: I am no expert on curves, worked it out as I went along. 10 years ago I accidentally set up a curve where CPU fan would turn off completely. That was a surprise the 1st time it happened. Case fans went crazy.