Usability testing: closed/open-ended tasks & actionable/verbal goals

I am building an app which provides users information about stocks and allows users to follow stock development by adding them to their favourites. I am planning a usability test and have checked some resources: Link 1 and Link 2. I have two questions.

  1. Closed or open-ended tasks? For example, I could have tasks like:
    • Search for a stock X and add it to your favourites (a closed task).
    • Search any stock from industry A and add it to your favourites (an open-ended task).

Which is better, or would it be good to include both types? I want for users to be able to explore the app a bit by themselves without too much limitations (open-ended), but I am worried if tasks then become too vague.

  1. Actionable or verbal goals? For example, I could have something like:
    • Check the info of a stock X, what do you think is the current status of this stock?

Link 1 talks about always having actionable tasks. However, I also want to test how users understand and interpret displayed information. So the goal in these type of tasks would be verbal, but I am not sure is this a good idea.