@julesha - welcome to Bubble!
While Bubble enables you to do many things, my recommendation is to build for simplicity first. As you validate your initial idea, then you can build additional complexity (ex. sub-domains) later on. (Sub apps and working with the API connector are great tools, but only once you have a well-established base product).
While ever situation is different, in most cases you should be able to easily and readily accomplish what you want to do with Option 1: build one app and filter views. Proper page-level redirects and database privacy roles should take you a long way. (For more context, I recommend viewing this post: How can a user only see his own data saved not others).
As well, as you’re exploring the concept of different types of users, this LearnTo lesson on Creating the Concept of an Admin User may be helpful.
Dan (creator of LearnTo - 15+ hours of Bubble tutorials and live coaching)