Performance will go up if the power limit goes up and cooling permits it
Based on other 6900xt card to date, I'd estimate every 50w to provide 3-4% performance improvement (as long as you don't hit the clock wall artificial amd troll cap) - so the 6900xt AIO is going to be 10% faster after max overclocking than the stock reference 6900XT (unless it hits the clock speed wall)
Wont touch a RTX 3090 is besically what you are stating. To go from 20800 to 21,632 is 4% more performance over the current maximum for the 6900xt. Then in DX12u performance will be poor compared to the RTX 3090 or 3080. A watercooled RXT 3080 (like the Asus rog strix 3080 gaming OC) will net you better overall performance. What tiny performance you lose in DX12 games, you get back in DX12u games.