I have a really good, sturdy crochet case for the only P's I am running, and a good loom bands case for change in case I need to run another P's I have. I don't use screen protectors, they obscure the view for me.
They scratch up very easily, that's actually quite normal for the TF and TFT versions to do. I think having a case helps keep your tama's shells pretty intact, especially if you accidentally drop them.I don't, but I am interested in them. Do they really help preserve the shells? I'm surprised by how terrible my Dream Town looks and I haven't been treating it roughly.