As you see on our demo site. All pages use HTTPS now.
We don’t use Really Simple SSL plugin.
SSL support is from your server (not from theme).
We install our demo site from Localhost to production by use Duplicator plugin.
Because this plugin will help us replace all data from HTTP to HTTPS.
If you see instruction use SSL use Really Simple SSL. It will have mixed content issues and you need manual fix.
That’s why we don’t use this plugin to install SSL.
Hope this help!