For a Full Strict SSL, I’ll have to install a certificate on the server-side, which isn’t possible on GoDaddy Managed WordPress hosting (According to the support team), so that’s not an option
I don’t think there are any mixed content errors, when there is no 521 error, the website load perfectly with a green padlock. I’d SSL enabled from the beginning of the site about 2 years. I recently changed hosting(cloned site) I don’t know if that made a problem.