Earths core and mantle producing plate tectonics?

Is that an interesting question? Science is about using the scientific method, in short, observe - analyse - hypothesis - predict - find evidence to refute prediction.

So questions about hypothetical -but untrue- situations are outside the scientific method. Anyway, plate tectonics is thought to believe the result of mantle convection, which in turn is the effect of heat produced in the Earth core by some mechanism. So hypothetically, if there was more heat generated in the earth core, you might expect stronger mantle convection and more plate tectonics.

But it remains highly speculative.

 

Again, the question is, the heat source, surely there must be some to a lot of radiogenic heat but some heat is also generated due to friction between the core and mantle due to irregulaties in spinning, see for instance this and this.

So if the size of the core was different, what effect would that have on the various heat sources? I don't know.