We know a lot about the dynamic of the relationship Rainbow has with AJ. Although there are a lot of tension between them, due to their competitive nature, they enjoy each other's company very much. I base this statement on their actions and body language. While on the other hoof we don't know anything about Bonbon and Lyra, except they are often seen together. Everything beside that is fan made speculation.

i think aj and rd make a good friend couple.

I agree with Mirage!

NocturnalMirage pretty much sums it up. Rainbow and Applejack are seen as friends and we know them very well. They may be competitive but they are great friends at heart. we don't generally see much about Bonbon and Lyra and not enough to fully understand their friendship

Apple jack and rainbow dash don't seem to have that much in common even though they are best friend

Because we know more about them, I suppose. All the main characters have been shown to be close friends, whereas background characters' relationships are often pure speculation.

I think they have quite an interesting and dynamic relationship; they have some similarities (such as being sporty and competitive) but they also have differences (Applejack being responsible and hardworking, while Rainbow Dash is more laid-back and mischievous).

We only know a lot about AJ and RD as friends.

They live together.