Where are block theme changes stored?

I apologize if I’ve missed easy-to-find information. I’ve made a lot of customizations to Twenty Twenty-Two. Recognizing that these may get deleted with an update, I’d like to create a child theme (or the modern equivalent) and customize the right way.

I haven’t done anything radical. Everything has been done within the editor. I’ve modified most of the standard templates and created a few new ones. I’ve created useful groups of structured blocks and saved them as Reusable blocks.

I don’t know where new/edited templates are stored.

I don’t know where template parts are stored.

I don’t know where reusable blocks are stored.

I don’t know how to ensure that those assets are not over-written with an update. It looks like the default configs and files are untouched. I’m just not sure without a deep dive into other folders or wp_options.

I don’t know how portable templates, parts, and reusable blocks are across themes : If we create a component while one theme is active, is it reasonable to expect that we can pull the resources into a different theme? I would think the .json files of a theme would be applied to assets, so we would get new color and font options (for example) with a new theme, but I don’t yet know what happens if we’re already using a style that doesn’t existing in a newly loaded theme.

It would be better for everyone, I think, if people could post references here to deep and current information, rather than taking the time to write it all from scratch here.

Thanks!!!!