I'm glad you mentioned Jujutsu. Given that it's also a git-compatible SCM my first thought upon seeing this post was how Sapling and Jujutsu compare.
Sapling, on the other hand, has much better support very large repositories, since they've spent a lot of time on that over the years. We're going to copy some of Sapling's solutions to Jujutsu soon, since we're working on integrating it with Google's monorepo (slides: https://docs.google.com/presentation/d/1F8j9_UOOSGUN9MvHxPZX..., recording: https://youtu.be/bx_LGilOuE4).
The Sapling support for remote repositories was a little rough in my opinion. Jujutsu and git-branchless can both co-locate with the Git repository, so you can always drop down to Git commands if there's something you're having trouble doing. (I find the `jj git` commands to also be better at interacting with remotes for now.)