I was just changing the frequency, again showing my total lack of knowledge of current BIOS configs lol. I've changed it back to auto now, the option to enable/disable MCR disappears when the frequency is set to auto so not sure if that means its still enabled or not. EDIT: Found the MCR setting eventually, disabled it and no change in behaviour when starting up
I haven't touched any EXPO settings myself yet, the DRAM profile is currently set to auto, which I think it using the JEDEC profile (4800, 40-39-39), but XMP1, 2 and 3 options are available, with XMP1 being the advertised 5600 40-40-40. I have tried setting it to XMP1, again no change.
I just checked the behvaviour when hibernating again, and it still shows no video when waking up from hibernate, however in this instance there are not BIOS lights up (The cpu fan/LEDs come back on however as does the keyboard)