Logan,
I am sure some current or former students will be on soon to share their perspective, but I’ll give you my quick take.
ATP is primarily a self-study program, hence the accelerated syllabus. You will have access to a student extranet account. That’s where all of your self-study lessons will be. Your instructor will also schedule ground lessons with you to verify that you are retaining the information, but it is mostly on you to hold yourself accountable. Take a look as this for more info: What does an ATP student need to do to be successful?
Each CFI may have their own style, but what I usually saw was CFIs would create their students’ schedules the day before based on weather, aircraft availability, and where each student was in the program. It is not expected that each student be at the training center until their lessons began, but it is expected that each student be available at a moments notice as things can and do change.
Tory