Two Topazes appear, non-speaking, in a flashback in "Now We're Only Falling Apart" alongside Pearl, Rose Quartz, and three Amethysts. One Topaz has her gemstone on her navel, while the other's gemstone placement is unknown. Four more are seen in the episode, "Familiar". The first two are seen guarding Yellow Diamond's extraction chamber, the other two are seen guarding Blue Diamond's pool chamber, each holding a mace.
Ruby (triple fusion) is the fusion of all three Rubies in "The Answer", one of which is the Crystal Gem, Ruby.
As their individual forms and gemstones are the same, their fusion remains identical except much larger in size. In this form, they are much more powerful. However, the actual extent of their strength in this form remains unclear because they fought against Rose Quartz, who is actually Pink Diamond in disguise. The Crystal Gem Ruby describes the fusion as just "me, but bigger," implying the state of being is not that different for her unfused.
So far, it is true that Gems of the same gemstone also share the same voice (with the exceptions of the Diamonds and White Pearl), albeit with some differences in tone. Their appearances are also nearly identical, excluding gemstone placement and minor outfit details.
Both Carnelian and "Skinny" Jasper were voiced by Kimberly Brooks, despite being two different types of quartz.
In "Hit the Diamond", it is revealed that Rubies are typically unintelligent and easily fooled. As Rubies are the Gem equivalent to foot soldiers and common enough to be effectively expendable, high intelligence isn't a necessity.
According to Ian Jones-Quartey, if the Pearls fused, they would form a bigger Pearl with combined colors.
This idea is shown when the Rubies and Topazes fuse.