For account types, I would save them in the database and map them into enums, so that if a new type is introduced or an account type is renamed, we just update the db.
I think there's no one size fits all, it depends on your project. I have been using Dapper for the past couple of years on applications I develop, I like the flexibility and the fact Dapper's performance is closer to executing SQL queries directly.
Another advise would be to avoid using .Result when running async methods because it does wait until the thread executing your code is complete, it is advisable to always await. Please see this.