Basically the idea is

Peach swaps with Mario

Daisy swaps with Luigi

Toadette with blue toad

And DK swapped with bowser.

Peach is a grocery shop owner and enjoys French cuisines.

Daisy is an ceo of four different businesses but lives in an apartment with peach (the two aren’t related)

Mario not even royalty his just a mayor. Dk just has beef with mario and has no real reason to kidnap him so much.

Luigi is luigi. Got kidnapped by ghost once.