Az, one has a mushroom head on the shaft, the other is a simple shaft. As the ends only bear against the back of the chain guide plate, I cant see that it would make much difference if you used an 18RG tensioner in a 2TG.
both engines used both types.
the slipper is designed to use one or the other.
mix'n'matchin might yeild an undesirable result. to tight or to lose even with adjusting it..
then again it might work just fine.
i always used
mushroom tip for mushroom tip.
and straight plunger for straight.