Yes, it is possible to use the programmatic functionality of Apptimize within an app developed with a unified build framework. Please note however that Apptimize's visual editing functionality is not supported.
Getting Apptimize working within such an app involves using our native iOS / Android SDKs on the native portion of your app, and then performing bridging / binding to translate the functions over to the non-native portion of your app.
You can find our general guides on creating the bridging / binding for Xamarin and React Native here.
Additionally, we have a working example of our Cordova plugin available for reference here.
We will be releasing a dedicated React Native SDK in the near future which will make integration into React Native apps even more seamless.