Same potato cpu I have tested with 3 different dimms (2x MFR, 1xCFR) and all max at the same. Wanted to make sure it wasn't voltages / settings hence 3 different dimms, but regardless, good old post code 23. Time to try another cpu.
VRM wise and in terms of oc the Impact imho is the best board of the ROG lineup. It's like the jack of all trades, unless you want to bench multi card then a full size board is needed. As you have said the only negative is the cold spreading over everything very quickly, other than that I would choose it over any other board in the ROG lineup.