I'll be brief - I'm offering a hypothesis if anyone can test it. The hypothesis is as follows: one should attempt to orient the heatsink so that the heatpipes are not going across both CPU core modules if possible. Examples below.
Not like this
Ryzen 1000-2000 & APUs...
Here is a simpler, less biased poll on the issue if you'd like to drop a vote. Feel free to elaborate on any choice.
Here are some source materials: