It's quite easy to use a theme.json for one theme with the templates and parts and patterns for another. I've developed a child theme generating tool to help you. Just visit https://blocks.wp-a2z.org/about/fse-themes-summary/generate-fse-child-theme/ Choose the Theme style and preview it eg Avant-Garde Then choose the Parent theme eg Twenty Twenty-Two, set a couple of other fields and you'll get a child theme when you hit Download ZIP.