Ok before I hit the hay. You can turn into an animal at will. Your clothes and such won’t turn with you but mass is not conserved so you can turn into something much bigger or smaller. It has to be a real creature that does or has existed and I guess if you want a plant that would be fair game. For me its an albatross. could travel around the world. might even manage to carry something that is not to large if packaged right. I am a bit torn though as the ocean is large so maybe a sea creature would be better. like a killer whale. of course then its not great for getting somewhere inland.
You can go back and forth between animal and human. Save on airline tickets by being an emotional support raven for someone and ride for free. No friend? Fine, buya human ticket and zhwooop, now and have a seat 5 times your size. Never wait in line to poop. Fill up with one meal. So awesome.
Plane crashes? Easy, just open a door as a human and transform in the air.
Raven is the winner.