I think the difference between if a ghost appears all messed up and gruesome has something to do with whether they have a shrine set up. This man with the cats and wife has a small room shrine to both his wife and two cats, and in Miko’s house they have an in house shrine dedicated to him as well. I think all the scary spirits are people who died without proper funeral rights and/or have no one to care about them. The ‘good spirits’ are probably using the shrine as a portal to visit from the afterlife or as a tether to continue watching over their loved ones.