Adding new users and managing them is easy. It is important to give the correct roles to the users. Please don't forget that there can be only one Account owner to manage the Plan and Billing. Based on your subscription model, you can have some Admins.
Most importantly, we offer unlimited users to help our customers to spread their brand guidelines with internal/external people and let them use the platform within the permission scheme. This is where the User Groups become important.
Last but not least, you don't need to invite people one by one. You can invite up to 100 people at once by adding a comma between the email addresses. No need to worry if there are duplicated email addresses since the platform shows a message in case of errors.