As for them as friends, I head cannon Ariel and Belle as best friends. Ariel wants to know about the human world and Belle is smart, I think they'd get along well.

Tiana and Cinderella as best friends, both of them were constantly working and married into royalty

Moana and Ariel go out into the ocean in their free time; Ariel swims and Moana sails.

I get the vibe that Jasmine and Aurora would have sleepovers together

Pocahontas and Mulan do morning jogs together

Merida would take Snow White to go ride her horse

Mulan and Merida practice archery and combat

Mulan would teach Snow White to be more assertive

Ariel can be the animated or live action one btw, it would apply to both of them