In which way this is different from PowerSync?
In my separate benchmark harness, Syncular currently does considerably better than the tested PowerSync setup. For example, 100k bootstrap is ~0.57s vs ~6.5s and offline replay ~35ms vs ~5.1s. Those are early results from one environment, though, not a universal claim (https://github.com/bkniffler/offline-sync-bench).
I've used PowerSync in the past with a huge initial bootstrap sync and was very frustrated by the performance back then (ca 1 year ago), which was one of the reasons to create my own library.
PowerSync is much more mature today obviously and still a great and proven tool.