-6, 96 bytes
Greeting=lambda n,rank='',formal=0:f"He{['y','llo'][f:=formal]},{rank*f and' '+rank} "+n+'!.'[f]Greeting=lambda n,rank='',formal=0:f"He{['y','llo'][f:=formal]},{f' {rank}'*(rank*f>'')} {n}{'!.'[f]}"- Greeting=lambda n,rank='',formal=0:f"He{['y','llo'][f:=formal]},{rank*f and' '+rank} "+n+'!.'[f]