re: WWII aficionados- were PT boats an effective part of the war effort?

In the right circumstances, yes. Early in the war they were hampered by shitty torpedoes, as was the case with both torpedo bombers, destroyers, and subs.

They came into their own during the Solomons Campaign where they had a degree of success in interdiction raids against the “Tokyo Express”. The Navy built upon this success by employing them against the supply lines of other Japanese held islands which were primarily supplied via barges.