I think it should be a combination of things. I think business casual has such a wide spectrum of options so I think a T should be dressed business casual in a way that is comfortable to them. I also think it is okay to dress in a way that reflects the comfort of their clients. I worked with a psych np who was very casual and used profanity. She is not somebody I would see because I would be uncomfortable. She had a lot of clients who adored her because she was on their level. They never felt judged.