Question about Sennheiser BT T100

Yes, that works without problems. In my case, I have connected a headphone and draw power from the TV box. Even this is sufficient for the transmitter.

I can confirm that the power supply is sufficient. Regarding aptX...you still have to expect a slight delay. If you only use one audio output, it's not a problem, but if you want to use the speaker on the TV and then others connected with BT, it might not be in sync.
I only use the BT transmitter with my headphones, so no problem. But if I add the TV speakers, the sound is out of sync.

I can confirm Ursari73's answer.
The problem with such systems (I have tried several) is the latency mentioned.
This is especially true if you cannot and/or do not want to switch off the audio from the TV.
You can get used to a SMALL delay compared to the picture, but compared to another audio source = like reverb in a cave :-(

Yes, the USB connection is sufficient for the power supply and pairing is quite simple. However, it is important that the receiving device (headphones or speakers) have the Bluetooth codec aptX if you don't want any delay or if you really want the picture to be synchronised with the sound...