As I have previously said, my posts are intended for guidance only and are not absolute. I believe you are tying to find scientific answers to your questions regarding tinnitus and the way it reacts. You won't find any because each person will experience the condition differently. People that have noise induced tinnitus do share certain similarities and I have previously explained this to you, particularly those that return to using any type of headphones after habituation. They risk making their tinnitus worse each time they use headphones, earbuds, headsets. At first everything may seem fine but things can suddenly change without warning.
Some doctors will tell patients that have noise induced tinnitus what they want to hear: using headphones is fine as long as the volume is kept low. The truth is these doctors don't know. Do not be lulled into a false belief because they are medically qualified they know about tinnitus. They are physicians and I believe experts in their field of medicine, but most know very little about tinnitus, particularly noise induced which they have probably never experienced.
I have noise induced tinnitus and have made it my mission to do my own research into the condition and what can make it worse. Corresponding and counselling people affected with it, I have concluded that using any type of headphones after habituation and being exposed to further loud noise, are the two main causes that make it worse.
Some people that have noise induced tinnitus use headphones, earbuds, or headsets without any problems. However, I have said things can suddenly change. Type headphones in the search box at the top of this page and read members posts. If you are looking for concrete surety that using any type headphones at low volume is safe, then I don't believe you will find it.
In my opinion, anyone that has noise induced tinnitus is risking their health using them.
Michael