• Different CPU and Memory needs to be used - 3 subs required

It depends on what different memory for you means, but otherwise it sounds unfinished. memory? Memory capacity, kit, or memory Type? These things differ massively. Also, Many users don't mention the specs of their memory in a seperate box for their submission.

Is there a clear answer?

as long as you don't use the same memory on different setups it's all good

So yes it can be the same brand but different SPD specs, different ICs, different memory size per stick,...