I read through your post a few times and it seems like you want the option to use your Persistent storage or just use the stick as a default install live boot medium.
If so, have you thought about using any of the live usbs with persistence and just make multiple users. One where persistence is used and encrypted and one that does not have access to the Persistent partition?
I’ve never tried it but i don’t see why not. Let us know what ends up working for you. Your English reads well to me.