The amount of heat a heatpipe can transfer depends on diameter, length, position and die size. In tower cooler heatpipes go from both sides of the base; it s basically double. These are the resaults on RX 580 (232 mm2) in vertical position; it can cool close to 100 W. If i raise power just a little bit, it couldn t stabilize the temperature no more. I tried it on i5 4590 and the resaults were similar; it managed about 100 W in vertical position (i dont have pictures).
Then, there is scythe ashura on rx vega 64. In vertical position it cools close to 400 W. Upside down, however, it couldn t stabilize the temperature (I aborted the test).