Choose the smallest useful combination
For a new presentation site, Thematis and Modularis are a useful combination. For an existing site, Modularis can work with its current compatible theme. Derivis is needed only when you deliberately want a derived theme.
In practice
Launch Packs create ordinary Pages and local media, not a separate site instance. Updating the plugin does not update installed pages. Reinstall and Uninstall explicitly inspect changes; review the warning before discarding an edited tree.