When developing on fs our own theme (including some scss from barceloneta), should we disable some bundle? This example shows "plone" bundle disabled. Generally speaking, it is not clear to me how it works on production, is my own compiled css with bootstrap, pieces of barceloneta, enough? Or do I need something else or disable something else?
If you have you're own theme active, only that theme is used for your site.
plone.app.theming is independent from the registry - so you won't find any barceloneta bundle in the registry.
The registry has js and css for additional functionality like widgets, sliders, ...