XFX say on their Website that the right position is the "powermode".
I have got the same Issue of too high Temps. Even after undervolting it reaches 80C.
I can tell u for a fact on my XFX RX590 the performance mode is to the left.The only thing the dual bios performance mode does is set a more aggressive fan curve.
Talked to XFX support and here is what they said. It is away from power connectors: