I get where youre going but not exactly. The dyson sphere would use solar energy but the fusion reactor, a tokomak specifically, uses steam generated by water pumped through the system to help keep the walls of the tokomak cool, to spin steam powered turbines
Just about the best way to do it for an external 'combustion' heat engine. Stirling engines can be used in some cases but in most cases steam ends up being the better option.
We spent centuries getting really good at using steam for getting work out of 'hot thing'.
Look into what Helion Energy is doing. Not saying it will or won't work, but they plan to extract the energy directly from the plasma electromagnetically.