Thanks!
Tinderbox (https://www.eastgate.com/Tinderbox/) is a great comparison—they have a different design aesthetic, cost a bit more ($249 one-time), but similar use case of deep knowledge work and thinking.
Endless Paper (https://www.endlesspaper.app/) is a sketching/drawing app, so not very similar to Muse.
On the infinite canvas point: this is one of the things we researched in the lab. Our studies revealed that it sounds nice, but in practice it's incredibly disorienting because you have no sense of scale. That's why we have a discretely-zooming interface; the difference is subtle but critical for high-speed thinking working.