1. Most common is AIDA64, you can also run 3DM Skydiver and note the Physics bench sections increase as CPU/RAM is improved. I do ~3 runs to get an average.
This post contains some of my test data.
2. Subjective. For me personally VID of 1.425V is MAX limit.
3. Some programs don't know if offset on X CPU is removed in UEFI or not. IIRC after UEFI 1401 the UEFI has temp offset removed. Even on the X CPU I own I use Sense MI Skew Disabled, then tCTL has the AMD +20C, tDIE in HWINFO shows it without and CPU sensor from Super IO Chip is correct so fan profiles works as needed. Example
link.