i didn't notice any audible hiss on mine with ANC on? tested in my bedroom which was quiet and also the kitchen with the fridge running next to me. ANC was able to block out all of the fridge running noise. then i had the Air fryer running next to me (which is pretty loud) and it didn't block out 100% but i'd say about 80% was blocked off.
with any sort of music playing you'll be able to block out airplane, bus noise easily imo. very impressed with ANC on this.
I hear pretty obvious hiss with mine, but I assumed that was the ANC as I can hear hiss in every ANC headphone I've ever listened to. FWIW the XM3 has the loudest noise floor of any TW IEM I've heard thus far, but again I think that's the ANC.