I can’t speak to Pamukkale, but drove in Cappadocia several years ago. Traffic was light and it was very easy to get around. I wasn’t on the look out for taxis, so I cannot comment on whether they are plentiful. While the sights were that far apart (maybe 15 to 20 minutes, they seemed remote with opportunities to stop for views and hikes off the beaten path. I would think a car would be more convenient, if you are comfortable with it.