Thanks! For now I'll just play with a 5V design to see how that works out. Isn't that what the isolated variants are about? For 20V there is a variant that mentions it's the same as the normal 20V, but in a P-well so you can "lift" the bulk. And, uh, any good resources to learn spice properly? I've mostly been using LTSpice and Cadence, so I'm not so great at writing manual simulations to get the plots that I want. Also... now that I'm starting to actually use eeschema a bit... I'm having second thoughts. The schematic editor is fine for small designs, but the ngspice integration is so basic as to be useless. I'm already struggling with things like... print the operating point, or... plot a current! It appears to only support plotting the currents of voltage sources. So probably going to give xschem another try.

The currents issue is more a spice thing than eeschema. By default currents aren't saved with the exception of sources as you saw. You can an option though to change this:

.options savecurrents

No luck with that. eeschema explicitly writes

.save

statements for things it considers worth saving, and adding your suggesting or

.save all

does not seem to change that. There also simply does not appear to be an option to write an expression to plot, so you can't do thing like calculate impedances and stuff like that.

Ah ok, that's frustrating