You can go back and forth relatively easily. I think that even if most of your views are still NSViews/UIViews SwiftUI makes sense even just to hook them up. ViewControllers are an anti-pattern.
Bindings might be better but that doesn't necessarily mean that ViewControllers are an anti-pattern. Is there a better way to do it in an non-declarative OOP way?
You should usually use a UIView instead of a view controller anyway (if you do UIKit programmatically, which is the only sane way to do it). Then it is easy enough. I have my own little layout library on top of AutoLayout, and at that point SwiftUI is nice to combine with UIViews.
