At the basic a CAL allow you to consume network service provided by a Windows Server, what this mean is that even if you have a Windows Server license it does not mean you have CAL (Per user or device) to allow access to the network services provided by this server.
So to answer the first part of your question yes you will need CAL, however the number of CAL you will need depends on your usage because from what I see you have more users than computers so you will clarify some points like do I have shared computers ? Do I use Microsoft 365 (Because you can have some CAL depending on your subscription) ? Which products are deployed in my environment ?
Below you will find a starting point regarding CAL :
This tool will help you understand a bit the kind of license you have in your environment :
If you plan to migrate some workload into the cloud you should investigate this link also (You will see a section with On-premises server rights) :