It looks like you have to get one that matches the exact make and model 3080 you have. I have a MSI GeForce RTX 3080 GAMING X TRIO on the way and am looking for a water block. Looks like this is the only one?
Alphacool Eisblock Aurora Acryl GPX-N RTX 3090/3080 Gaming X Trio
I don't know, I've had my 3080 for a while now and it doesn't make any noise. That makes me think I could overclock it but when I try with the MSI afterburner it can't really do anything nothing seems to change. If you can fit one of these gigantic over-spec cards into your case I don't think you need to water cool, for sound anyway.
Mine is fairly loud. Not awful by any means but plenty of room for improvement.
It looks like the EK backplates have finally arrived. Hopefully I get mine next week, but the following week seems more likely. I'm really hoping I don't run in to the coil whine issue others have. Evidently the EK backplate can amplify coil whine to quite a large degree on the XC3 cards. I have some 5mm thermal pads ready to go if needed; can't say with any certainty they would help though. Worst case I'll just run the card without the backplate and hope someone finds a solution.