ScalaFX is a DSL for working with JavaFX. Offering, what you call "syntactic sugar" is the main purpose of a DSL.
(A DSL traditionally also limits the scope of the host language to the target domain, but that is usually not desired of Scala DSLs.)
Now, how and when that is useful, is a debate in its own right, but that is essentailly all that it is offering. Personally ,I would always prefer an API that lets me communicate my intent more clearly to my peers and my future self, but that is something, that every team and project has to decide for itself. The binding syntax of ScalaFX is wonderful because Properties and Bindings are finding their way into more and more backends (even without a JavaFX GUI).
The reason why ScalaFX is advertising type-safety, I think, is not because it is a special feature of ScalaFX itself, but because it is noteworthy that using such a consice, script-like language such as ScalaFX and leveraging the power of the platform that is Scala, will still give you type-safety (which might be counter-intuitive to newcomers and people unfamiliar with Scala).
I would recommend using ScalaFX in your case ,as it sounds you are working on a small project , which mainly is focused on the user experience delivered through a JavaFx GUI ( I assume given your description). ScalaFX will allow you to iterate quickly on the GUI.
Don't worry about overhead in the beginning, your use case will hardly be a performance-demanding app. If you do need to worry about performance, why are you using Scala ;)?
The biggest downside to ScalaFX is that every JavaFX type needs to be wrapped with a SFXDelegate, which is cumbersome if some type you need is not wrapped or in the future something gets added to JavaFX and you need to wait for ScalaFX to wrap it before you can use it ( both of those are no real blockers though as firstly, it is trivial to wrap a JavaFX type (see the ScalaFX Wiki), and secondly the release cycle of JavaFX is much slower than ScalaFX's.