I've decided to do some focused study on a few lines of play, mostly new joseki etc. In the pre-AI days this would involve firing up the database and printing off some game records of interest. Is it possible to do something similar with AI? I'd like to have KataGo (or some other AI) self-play a game from a given starting position with some reasonable number of playouts. It must be technically possible, but I'm unclear on the mechanism.

Has anyone had any experience or success with something similar?

You can do this in Katrain with the "fast playout to game end" menu item, which has the shortcut key "l". This will playout a game using the number of playouts you have configured for "fast analysis".

In my experience there often isn't much variety in the first tens of moves. I haven't found much use for this.

When I did something similar a few years ago, I used GoGui, plus python scripting to automate parts of the process. It's interesting to compare what different AIs choose in the same position.