Yeah the back and forth thing is normal, my dentist went back to them with feedback as they recommended shaving some enamel on my first plan & she said it’s ridiculous as I’ve got good healthy teeth and it’s a minor course there’s no need to make permanent adjustments to teeth. The next plan was entirely different based upon my dentist’s feedback, you have to remember they don’t actually see your teeth so it’s going to have to be a collaboration between the two!
Re loose teeth - horrifyingly my dentist didn’t tell me til mine were fitted. She said it’s normal as the bone needs time to catch up with the movement, I’m really glad I’ve not experienced it but I’m constantly anxious I’ll pull a tooth out with my retainers

the only answer to that is keep them on as close to 24/7 as poss