In short: My XFX SWIFT OC 9070 XT could only do -60 voltage offset with 2700mhz memory clock at +10PL with the Performance Bios and the performance gains were only 1-3%.
Switching to Silent Bios did wonders for me.
Now it's stable at -120 Voltage Offset with 2800mhz memory at +10PL.
For 30-32w extra I'm getting 8.5-10% MORE PERFORMANCE at slightly lower temps which is great.