a Ryzen 7, Yuzu barely uses it, at most 30% utilization
With emulation, that's usually an indication that not all cores are utilized. The most faithful emulation is to use as many cores for the CPU as the original system has. From Wikipedia: https://en.wikipedia.org/wiki/Nintendo_Switch#Technical_specifications
While the SoC features 8 CPU cores, the Switch only uses the 4 64-bit Cortex-A57 cores, of which 1 is reserved to the operating system
As you can see, only 3 cores are actively used by the game under high pressure. The one system core is probably (just probably!) light on resources to emulate. I don't know how many cores your system has, but this should be an indication why only 30% of your CPU is utilized to emulate the game.