Number of cores and maximum memory should both, by default, be left unchecked. Those should never be changed or altered IN ANY WAY except in very specific circumstances for very specific troubleshooting purposes. Under normal troubleshooting conditions or normal operation, nothing in MSCONFIG should be altered AT ALL. If you want to stop or start services, or change the operational behavior of a service, it should be done in administrative tools services applet, not in msconfig.
So anyhow, yes, that should be unchecked and it should have been unchecked from the start. Was it not. Was there some amount there before?
I know you mentioned the BIOS updates, but lets verify. What is the current BIOS version shown to be running when you go to the main page in your BIOS startup configuration screen?
I personally would find a decent B450 motherboard and try the memory with that. I think you'll have more success than with that really cheap board. But if for any reason you still have an issue, I want you to be prepared for that possibility because there are no guarantees, EVER, even for the most experienced system builder or repair tech, when it comes to making a diagnosis of the motherboard or memory when something isn't working right, but is working. Much easier when something doesn't work at all.
Otherwise, you might want to simply take it to somebody who IS able to help try and configure the memory. I think I'd try a higher quality board first though but of course that's up to you.