I will clarify the simulator issue.
If you use a "fat" framework, that is a framework that includes binaries for i386 as well as the arm binaries, then the ipa file will be rejected when you try to submit it. The reason is that swift libraries are dynamic libraries and unlike regular static libraries they are embedded as-is in the app. The app store verification process rejects non-arm binaries.
You can use a fat framework during development and switch to an arm only framework before submitting it to the store.
In the future the B4i builder will automatically strip fat dynamic frameworks when you create a store build.