I sort of covered this in my other reply, but yes, switching losses are also due to electrical resistance in the semiconducting transistor, and yes I’m assuming that semiconductors are replaced with superconductors throughout the system. Electrical resistance is pretty much the only reason any component generates heat, so replacing semiconductors with superconductors to eliminate the resistance will also eliminate heat generation. I’m not sure why you think superconductors can’t be used for transistors though? Resistance isn’t required for semiconductors to work, it’s an unfortunate byproduct of the material physics rather than something we build in, and I’m not aware of any reason a superconductor couldn’t work where a semiconductor does in existing hardware designs.
Then again I’m also not an IC designer or electrical engineer, so there may be specific design circumstances that I’m not aware of where resistance is desired or even required, and in those situations of course you’d still have some waste heat to remove. I’m speaking generally; the majority of applications, GPUs included, will benefit from this technology.