I can't speak to oz's error messages, but for the vega-lite + python integration, I've found altair pretty usable. In particular, simple scatter plots with tooltips were easy to get up and running.
Thanks for sharing. I may do this if I ever decide to do some 'notebook' style work. Oz mentions integrating with jupyter and whatever else, but I love org-mode and wouldn't really want to start using a tool other than Emacs if I could avoid it :)
To be clear, there isn't really any org magic going on. You can also do the same identical stuff directly from a REPL and just spit the SVGs to file.
I've also used the same stuff in a GUI - where the SVGs are rendered directly in the UI (I just parse the SVG elements and draw to the Canvas)
Oz/Vega/etc. innately have this blackbox JS layout/rendering layer which I'm weary of. Here you are just manipulating SVG hiccup directly in Clojure. And then at the very last stage it's exported to SVG's XML syntax.
I've only done a simple line chart so far, and I used this oz library for interfacing with Clojure and displaying results in the browser. [1]
One of the problems was lack of error messages. Not sure what part of the tooling was failing me there.
[1]. https://github.com/metasoarous/oz