Org Mode and Observable are both performant enough. Unfortunately, they have their own limitation. In Emacs+Org Mode, you're working with a rich text display as a canvas, so while you can output images easily, forget about interactive GUI (charts, control sliders, what not) - at least without some dark hacking magic.
Observable - that's a true joy if you want fast feedback and interactivity. It's as fast as your browser, since your notebook is entirely client-side executed JavaScript. It's an order of magnitude better option than regular notebooks if you want to do some exploratory or scientific visualization. It's main drawback: JavaScript. That's what you're limited to. So forget about your favorite Python or R libraries (at least without dark hacking magic).
