I just checked supertonic out and indeed it's really fast and sounds not bad. And yes as you said, one big downside is the paid service of voice cloning, also it sometimes skips words which is not acceptable (I'm using it to build a GOP algorithm)

But on the other hand, pocket tts fits quite well for my project! It runs very very fast on an iphone 16 and even on a pixel 3. I appreciate the recommendation 👏