Theme setting to change block position (region)
First of all you should change each desired block region for your theme manually at Administration&gt;Structure&gt;Block layout Tab and then go to the config export function at:  Administration&gt;Configuration&gt;Development&gt;Configuration synchronization&gt;Export Tab&gt;Full archive to export all the block settings for your theme.
Then you should take a look at to the generated YAML files and placed them in a new folder within your theme at /config/install. you then uninstalled the theme and then reinstalled it as the default.