A short and concise presentation by Robert Hallock (Technical Marketing Manager of AMD) describing XFR and PBO:
https://m.youtube.com/watch?v=426hLGoXDbM
You would probably have to enable it in the BIOS (UEFI).
Whether you should manually overclock all cores, or purely rely on XFR/PBO will depend on your main workload for the CPU. If you're mainly gaming, then enabling XFR/PBO (not manually overclocking) is likely to be the better option as games don't tend to make great use of all the cores and XFR/PBO is likely to be able to auto-boost individual cores to higher frequencies than a manual all core overclock.
If you enable XFR/PBO, make sure you monitor voltages and temperatures closely, because your motherboard could potentially apply some unsafe voltages. Probably unlikely, but better be on the safe side. If you are manually overclocking, I assume you'll already be keeping an eye on the voltages and temps anyway.