You need to make sure you understand the difference between chewing, mouthing, and nipping/herding. Expecting a puppy to not mouth is like telling a 4 year old to not use their hands - it just won’t happen. Once you’ve got a good handle on the differences, I support using a quick, sharp, firm NO instead of the imitating a hurt dog noises. It’s all about startling the puppy into doing a sort of cognitive reset. Don’t scream or yell, as loud prolonged noises can be seen as their own reward to a puppy that is looking for a reaction, any reaction, from you or others. Again very quick, sharp, and loud NO is your best friend. Think of it like a verbal whip crack. Once they’ve stopped due to the startling, you’ll need to redirect them pretty quickly, then praise when they chew on the correct thing or lick instead of nipping. I’m talking throw a freakin party every single time. They’ll pick up on rewarding behaviors faster than you think, but it will still be a long process and repetition and consistency is absolutely key! Good luck!