Can my EVGA psu 600b 80+ Bronze power the MSI B450 Gaming Pro Carbon? Or do I need to get a new PSU for the extra CPU power plug.
One 8-pin CPU power connection is plenty even for the 2700X. So yes, that PSU will be fine. (I might choose a different PSU but that's a different question.)
I thought about getting CORSAIR RMX Series, RM750x.
Well, the Corsair RMx series (regardless if it has one or two EPS CPU power connectors) is the better unit.
But other than that, as kschendel mentioned above, you only need to connect one 8-pin EPS connector.
So, if you wanna buy a better unit that's fine, but not buy a PSU because it has 2 EPS connectors. :)
I got the RM750x
Congrats, you just bought a rock solid PSU that's quiet and comes with a 10 years warranty! +1