Yes. They give you boatloads of coins, and they're borderline required if you want a good shot at getting Phlox.

Yes. How else would you get them?

If anything just buy the rares

Significantly easier to get depending on where you are in the game, and they produce more coins than their common counterparts

What Shint said, the Rares are much easier while also being better.

I’d say the most worth it on each island is Tiawa on Light Island, Bowhead on Psychic Island, Krillby on Faerie Island, and Incisaur on Bone Island respectively.

Honestly? Just try get them all if you can, they're all good for multiple reasons lmao