Not a physicist but my understanding is superconductors have max amount of current you can put through it, so its not clear it can be used for free energy distribution at scale even if it is a super conductor.
Even if it allowed infinite current, the only thing that would become "free" is what we currently lose to inefficiencies in the conductors. There's still the cost of generating electricity, maintaining the distribution infrastructure (which would likely be far more expensive than what we have), etc.
Cheaper and smaller than what? All the existing fusion power plants?
We have to make it work before we can optimize it. Fusion still poses many engineering challenges that have nothing to do with the quality of our superconductors. How to not melt the reactor walls and what to do with all those angry neutrons, for starters.
Cheaper and smaller than all the existing experimental fusion reactors such as Wendelstein 7X or the under construction reactor ITER.
The vast majority of their size, weight, and cost is related to maintaining extremely low temperatures for the superconductors right next to the angry neutrons.
If you could use a regular coolant loop with heat pumps and only needed to maintain, say, -20°C, it'd be much easier to keep the superconductors cool and transport away the neutrons' heat.
The neutrons are an issue because they slowly destroy the reactor materials [1].
Point is, even with better superconductors we'd still be a long way from practical fusion power. They'd be a step forward, but they're not the key that's going to unlock a world of cheap clean energy.
