Depending on how rich in internal radioactive sources of heat it isn't scale free with mass. Larger masses of the same makeup will reach different thermal equilibrium since the surface area grows at a slower rate than the internal heat production from decay which scales with mass.
I don't know if it is significant, but tidal sources of heat might not scale the same either.
Yes it's small, but:
At least during emergence of life there was the faint young sun + higher proportions of radioactive elements, so could have made up 0.2% of outgoing thermal radiation or so on earth (ignoring outflow of residual heat from early collisions). I think 5-10 earth masses is the limit for terrestrial planets, and you can imagine having say 10x more radioactive elements and still hospitable to life, rather than being made of solid uranium. So maybe double digit percentage radiant heat outflow differences between very small and very large on those.
I think we can safely say the planet made of uranium is an edge case.
The Earth's internal radioactivity is a miniscule energy source compared to the sun.