Bluetooth is used for a number of things, and how it interacts with hearing aids is complex. If you want to get right into the detail of it then here is a good article to read.
The first use is to use a smartphone as a remote control for your hearing aids. That is a nice to have, but not totally essential. Some apps for hearing aids are better than others. Generally the most mature technology is the Apple MFi which used Bluetooth Low Energy to save battery power. It is also able to connect to both hearing aids at the same time.
The next use is to be able to use your cell phone with the incoming audio coming direct to your ears. That feature, at least with the iPhone MFi method is very helpful. Typically the hearing aid can be set up to recognize that you are streaming direct to your ear, and the HA microphones can be set to attenuate background noise which makes it easier to hear. Some hearing aids like the Phonak or KS9 cannot do this because they use the HA microphones to pick up your voice. So the person at the other end hears you and all the background noise. On the down side, the MFi method requires you to hold the iPhone close to your mouth so it picks up your voice clearly. It is not true hands free.
Last is the streaming from the TV or other devices using what most likely is classic Bluetooth. Most of those solutions involve using an intermediary device which ideally converts the higher power Classic Bluetooth to BLE or Bluetooth Low Energy. This makes it easier on your hearing aid batteries. But, have a look at my audiogram. If your loss is no worse than what I have in my right ear, you will probably have no problem hearing the TV at normal volumes.
Hope that helps some,