Hi ,
Microsoft licensing eco system for Dynamics 365 Application stack especially for Dynamics 365 F&O has gone through a huge change. Now licensing is effected by what kind of roles , duties and privileges are assigned to a specific user but by the use of that particular module or functionality.
For e.g There is a user Sam who we have assigned the role of Project Manager , Accountant or supervisor and if that Out of the box roles has duties related to Project Management or related to it then it will definitely consume Project Operations Attach License whether he or anyone in his organization opens Project Module or not.
In System Administration Module you can easily view the newly added role based reports which will give you a better clarity before you want to decide to buy a license.