I use super tweeters with my TAD speakers. Tad’s are quite extended with a beryllium tweeter so there is really no technical need for a super tweeter.
Just a few days ago I decided to cover the super tweeters with something to temporarily see how the system sounded without them.
It was quite a difference and definitely reinforced my decision years ago to add them. Mine are Enigmacoustics Sopranino permanently charged electrostatic.
Not sure if they’re made any longer. The thing is once I got them I felt the system was a little out of balance and decided to get subwoofers to extend the lowest octave. Extending the frequency response on both ends aids in the realism significantly.
I also think as we age and loose high frequencies it’s helpful to augment them.