Note: Keep in mind, there are training seat costs for the exams based on having a training seat allocated to your login from your organization. If you don't already have a training seat allocated to you, you can work with your Nintex sales representative to get that setup in Nintex Customer Central.
The Practitioner level exams may be available to you already. If you do not see the Expert level exams then you will need to work with your sales rep because they have an additional cost.
The K2 persona based exams (e.g. IT Developer, Citizen Developer, etc.) apply to both K2 Five and K2 Cloud.