yeah, unfortunately I think in my particular case an electric knife wouldn't work. I make homemade American process cheese, and it's
very soft, so I'm pretty sure that it would still stick to an electric knife, as well as tear really badly. From the videos, these ultrasonic knives seem like they would work perfectly but the commercial options are all impractically expensive and from doing a little research, all the DIY versions are tiny blades meant for cutting stuff like plastic on 3d prints etc.
Apparently getting the blade design right on a bigger one so that it properly resonates with the transducers is tricky.