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.
Yeah my intention was no real gotchas outside of whats listed. so you could effectively disapear as you said as a fly but your clothes and such would fall and you would be naked when you turn back. Honestly the clothes effect would likely that much more make people think you vanishe or teleported or were destroyed or something.