Hello.
First of all, we're talking about "saving licenses" ..just it.
there is no "right way".. but in the case of assigning licenses to these mailboxes, you can select another type of licensing, such as Exchange Plan 1 or even a Kiosky license. Which would save you some money.
however, when converting these mailboxes to shared mailboxes, there is no need to use a license with them... and they are commonly used in exactly this situation. (department mailbox.. HR, support…)
Regarding the use.. the share mailbox does not differ from a mailbox to a mailboxuser
With the automap active, once permission is given, it will automatically load in the members' outlook.
Take a test, create a sharemailbox and assign it to your user and you will see.
No license required..enjoy