Your own domain name and the version of your website are 2 distinct things.
On all types of SimDif sites you can purchase your own domain name with YorName.
Enjoy a fair price, a free https (SSL), keep your independence, and have the possibility to use this name with another service if you see fit.
To purchase your own domain name, go to Site Settings and look for "Site Address - Domain Name".
Select the green button "Purchase your own domain name with YorName.com".
Pro sites also allow you to link a domain name you purchased from another registrar.