I tried both levels for instance.. I have set 1.32500V in bios
Level 2 shows me 1.296V in CPU-Z during idle and 1.312V on load,
Level 1 shows me 1.296V in CPU-Z during idle and 1.280V on load
Based on my experience any way you choose it it's all matter of tuning. You might have to up your Vcore if you use Level 1 to get it stable and Level 2 might be just the right thing.
I'm still experimenting with Dynamic Vcore Adjust (DVID), as it seams interesting as well. :)