since the card cost a fortune and one way to lose you money is to fry it.
I advise 270 watts and 2150 memory
vs 300 watts and 2400 memory
check what that drops the hash to 110 hash is about 12 a day usd
115 hash is about 12.50 a day usd
120 hash is about 13 a day usd
if I were you anything over 110 is decent only 1 dollar less a day before power cost. and may save the card.
also a fan blowing on the back of the card is good.
I'm not sure why but it seems like 3090 is more power hungry than memory hungry when it comes to hashrate. Played with memory a bit and seems like changing it to 2000 from 2400 or 2600 doesn't bring much change to hashrate but the power does. Bringing power down even by 5 makes hashrate goes down by 10-15. So as per your suggestion I did 280 on the power as 270 gets it down to 105mhs and bought down memory to 2100 and I'm getting 112-113 mhs. You think thats ok for the longevity of the card? Thanks