I don't remember Tuvok's rank insignia, but I am pretty sure he was called "lieutenant" throughout the show, and I dimly recall that at some time or other fairly early on, a reason for this was given. He'd lost rank because he'd left Star Fleet for some reason or other, maybe? I just can't remember. But I do remember a specific conversation between Janeway and Tuvok in either the first or second episode in which Janeway explained why she'd named Chakotay her first officer over Tuvok, and it was to promote unity between the Star Fleet and Maquis elements of the crew. Also, Chakotay did have the qualifications.
But I don't remember the insignia pips. Gladys Knight and the Pips, yes.