f I pay monthly, does that mean I get a certain number of submissions a month?

Further, I am confused about the pricing. If I pay monthly, does that mean I get a certain number of submissions a month, or is the number given the total despite monthly costs?

The Submissions limit is a monthly limit. The submission counter will reset on the first day of each month. The limit is different for each account type. You can check the available account types and limits on our Pricing page. I would also suggest you to check this guide:

Understanding Your Account Usage and Limits