Might also be fun to test this with a variable (but static in test) load - How well does the change in orientation affect a 50W processor versus a 75W versus a 100W processor? This can be done fairly easily by modifying the processor's current limits in BIOS.
I kinda did this in my previous tests. Not by limiting the current in BIOS but using different static load scenarios resulting in different power draws of the CPU.
For my Ryzen 3800X I found that there is no performance impact as long as the temperature stays below 81C. Once it reaches that value the CPU (BIOS / motherboard) starts to reduce clock speeds / voltages. So my conclusion is: any orientation is fine (performance wise) as long as you (your cooler) can keep your Ryzen below 81C.
Not sure where that limit is for Intel CPUs or different graphic chips. Maybe we can still collect some more test results here.