Turns out that the GPU clock was unstable at settings higher than +145. From there it pretty much depends on the fan-curve/speed how many points you get in a benchmark. Cooler GPU means higher average/persistent boost speeds and thus higher points. For example, getting over 5000 pts in Superposition is mostly a question of fan vs. noise for me, not so much of the last few ticks of GPU clock.
The fans on the Asus Dual become quite audible above 40%, especially because they tend to wobble a bit (visible and audible) and have changing acoustics even when they are supposed to run at a fixed speed. The VRM section can get noisy during certain loads, too.