Can someone explain in simple terms whether I need or should enable AMD EXPO?

[mortar_user_64GB]

It depends on the voltages in your particular case (CPU + RAM + Mobo + PSU).
So even if you'll find someone with the "same" 4 components, the voltages won't be the same as yours!
In any case, the safest route in case of instability is to use the EXPO settings, but set the memory speed to 5600MHz.

and i guess over time, with BIOS updates, these instabililty issues to do with RAM will be resolved

 

[RemusM]

and i guess over time, with BIOS updates, these instabililty issues to do with RAM will be resolved

With the current AMD CPUs and the current VSOC limitation don't expect for miracles.