The cool-comp gpu block, (pictured earlier in this topic), may have fitted but I don't think so once the tubes are fitted due to a capacitor on the card. I also wanted to use the fan plug header so the plug and wires would definitely be in the way. other cards have components in this area also.
I didn't liquid-cool mine for overclocking purposes but more towards the fan free silent PC goal. I never checked the newer Asus for difference between air & water, but the original, (was one of the first Asus GF3 cards), and would get slight artifacting at 230/535. I would get occasional lock-ups at higher core, ram would go to 545 before causing a lock. After the liquid cooling it would do 260/560 any higher would cause lock-ups but no artifacts. Newer card will do 275 / 575 without issue and no volt mod. Planning on doing the volt mod soon. Worth remembering my coolant is currently 12°C and I get nice card temps reported by the Smart Doctor app.