Finding out which Azure AD accounts have licenses (service plans) for different applications isn’t difficult. You can do it with either PowerShell or the Microsoft Graph API. This article explains how to use PowerShell (and the equivalent Graph API call) to find accounts which have a certain license (service plan) enabled or disabled. Once you know how to navigate license data in Azure AD accounts, you can take the code and adapt it for different purposes.
The Office 365 Admin Center includes reports of licenses assigned to users. The same information can be extracted with PowerShell, which means that you can analyze license assignments anyway you wish. The script is quick and easy, mostly because its error handling is non-existent, but it’s enough to get going.