Using Copilot on a Delegate Mailbox

Question

Microsoft recently announced support for users assigned "full delegate access" to use Copilot to search the contents of another user's mailbox. The article noted that:

My QUESTION is: What does "full delegate access" mean, specifically?

1. Can the mailbox owner simply go to File > Account Settings > Delegate Access and assign another person EDITOR (or) AUTHOR (or) REVIEWER (or) CONTRIBUTOR rights? Do any of these permission levels equal "full delegate access"?
2. 
3. If the permissions available under File > Account Settings > Delegate Access do NOT give the delegate "full delegate access"-- what is the SPECIFIC permission level within Exchange that a delegate would need? Is it "Full Mailbox Access (FMA)"?

Thank you for any assistance in clarifying this issue.