Monthly, or Annual... paid Monthly?


As a CC user, I would like to try out Adobe Stock, but I really don't need to subscribe on a regular monthly plan.
Now I've seen these two plans, but need to confirm the difference... other than the price!?
Question 1: What is the difference between Annual plan, paid monthly and Monthly Plan? Is the Monthly Plan, just a one off payment for 350 standard images?
Question 2. How long do I have to download the 350 images... would I have to use my quota up in that month?
