Can you use delegations if the Participant type is "A person"?

Yes. Regardless of the type of participant (i.e. A person, A list of persons, or A list of persons with coordinator), you can use delegations.

You can delegate a user’s role to any other user that has been added to WorkflowGen even if the delegatee is not part of the same process participant list as the delegator.

In fact, the delegatee does not need to be part of the process in question to be selected as the delegatee by the delegator.