A blueprint is a subclass of it’s parent, it is not an instance of it’s parent. An Actor in the world is an instance of whatever Blueprint/Class it is derived from.
So when you specify TSubclassOf<AMyActor>, any valid value for that is any subclass of AMyActor, as well as any blueprints that are derived from any of those subclasses. This is what the editor shows you.
Once you have a TSubclassOf, you can spawn it into the world, or whatever. You don’t want to be trying to access values inside it, though, unless you need to know it’s Defaults.
I don’t understand how this has anything to do with your other stated issues – it shouldn’t be related.