I plan on undervolting my 3090. Should also help with idle wattage, which is good as my gaming PC is currently my work PC so is on all day.
I spent some time undervolting my 3090 FE on the weekend. The results weren't quite what I expected after undervolting with a 3080 ftw3.
With the 3080 I found that 1965 @ 0.962V basically maintained frames and benchmark scores vs overclocking and using the full 450W power budget.
With the 3090 FE I found that Port Royal took a big hit, but actually gaming (Borderlands 3) was just fine.
The reason is that Port Royal seems to draw much less power on average (oddly, as I thought that ray tracing workloads generally drew more), meaning that the card could go hit high clocks by using over 1V.
With Borderlands 3, and other games, I'd imagine, the power draw seems much higher on average, meaning the card can't scale the curve and hit high clocks anyway, with the card hitting power limit between 0.9 and 0.95V most of the time.
Where as with the 3080 the limit was really stability at higher clocks, with the 3090 it is overwhelmingly power. So I guess it depends on the specific workload, but undervolting seems like a win in some and a loss in others.