You need to reinstall your apps (restore from iCloud is the easiest way) to get the repackaged app version.
Then have fun with 2nd/3rd party apps. And yes, the speed improvement happens on all devices (from the 6s to the Xs, iPads too).
When all of this was enabled fully internally I spent half a day just doing A/B launches with the excitement of a kid on Christmas Day.
For frameworks you use rarely:
- do not dlopen;
- do not use static initializers, but lazy ones (pthread_once/dispatch_once)
- avoid duplicate class names like the plague;
- try to put categories on the same class in the same binary (if you extend say NSString 3 times, do it from a single binary if possible)
- avoid swizzling during launch (or at all really)