Both of the fusions we've seen of Garnet (not including Ruby and Sapphire) have had some sort of special visualization. Sugilite had some sort of dragon breathing fire, and (Spoilers) had a (Spoiler) visualization. We haven't seen Alexandrite's actual fusion, but I assume its the same way. All of the other fusions are just basic light-form melding. I think that any fusion involving more than 2 Gems get these kinds of special visuals, although for what reason, I'm not sure.
On a related note, both of the fusions we've seen with Pearl show that her dances are more involving of the other partner. When Garnet and Amethyst formed Sugilite, they were dancing on their own until the finale, whereas to form Opal and Sardonyx, Pearl actively went to her partner to continue the dance.
Okak, so he replied to the questions:
1. "Are Gems (excluding Ruby and Sapphire) polygamous?"
2. "Can you tell us anything about Homeworld?"
He responded: "Those are both spoilers, sorry."
I can understand the Homeworld one, but why would the answer to whether Gems are polygamous be considered a spoiler? Would that have been revealed? Because if it was a spiler, that means that it would be revealed in the show. Can we conclude then that it is true?