my experience

Must notify HR? NO
If you still work for the same company, you are H1B/AOS dual status. Your H1B is still valid

Renew EAD?
Yes, you can do it yourself. Super easy. Just fill the form 765 (only 1 page), 180USD, 2 photos. I did it 4 times.

If you change company, you are no longer H1B. You become sole AOS status.
You can still renew it yourself. It is safe to renew it 100 days before expiration.