Two fire signs together are pure intensity: passion, initiative, zero boredom. You understand each other's urgency to live. The obvious risk: two flames compete for the same oxygen — learning to yield center stage is what makes this last.
Two mutable signs: infinite adaptation, mutating conversation, plans that change without drama. The hard part isn't getting along — it's deciding. This bond does well when someone says 'this, here, now' once in a while.