1. Self study all the way, however, there is one exception though, based on my observation if a teacher is a female and beautiful, that really helps with my concetration and absorption of the contents.

All our German professors are females and really beautiful so classes are always full of students and there is always a pin drop silence. I think our course director has done his homework
They are all Phds. You can not be a lecturer in a german university without having the Phd. It is like an icing on the cake.
2. If a teacher knows how to teach the language then why not. He/She can guide you properly and provides feedback on your errors.
However, I find it such an approach slow going so even I have decided to work with a professional teacher I still have to put in the extra yard by myself.
3. I have listened to thousands of hours of audio by myself. Since I am living in Germany, I instantly get feedback on my listening ability. Some German speakers at shops and pharmacies were not understanable a few months ago; they are now understanable. Some sort of processing is happening behind the scenes. You can not discard self-study altogether.
4. It always depends on your learning style. I can not do drills after learning a grammar rule. I have to see them in real context to absorb them. Instead of doing grammar drills, I create short stories with a particular grammar point, of course, with the help of ChatGPT.
That;s how my brain learns. If a teacher is teaching grammar rules most of the time then throwing in exceptions of rules in between, my brain feels like I am studying calculus. Unfortunately, classes are full of teaching grammar rules. As a teacher , easy to design and follow them.
5. Finding a good teacher who can also understand the mechanics of your brain is hard to come by.