Hi @bmndan,
I don't know if the process I shared above migrates the themes and plugins. It seems that it migrates the different post and media to the new site. If you also want to migrate the plugins, you will probably need to use a WordPress' extension like this one
https://servmask.com/products/multisite-extension
You can ask the developers of the extension or the developers of WordPress to know more about it or other possible alternatives.
Thanks