L1GHTNING

Be sure your OC is turned off in the Radeon software before you do it with MSI Afterburner. 

Found it ! Had to go into Manual just to find the option. Will definitely turn it off thank u.

always add more frequency if voltage stays within 1.3V, instability will force you to back off anyway

Just use offset mode for voltage instead of manual and apply negative offset to drop the voltage. LLC should be set to auto (disabled).

PBO is better than manually setting a fix clock speed but you still have to monitor its stupid voltage decisions.

I'd stick to 1.3v for now, until we get more info on how 7nm survives 1.35v if not 1.4v.
 
Tho for overclocking, you should do everything to the memory first, then touch the CPU settings. Have you tuned that up yet?

1.36 volts max for a 4.3GHz OC is incredible, lucky chip you got there.
 
Perfectly good to run daily if voltage is sub 1.4

for 1440p you need a stronger GPU instead of CPU only like 1070ti/2060 etc.

I got B450 and its cold on 4.2 oc ryzen 2600 and yes should be fine with ryzen 3xxx series