Installation Question

Ok so I have just bought a server that will have Centos 7. It should be ready be middle of next week and I want to install Virtualmin when it s up and running. I have read ahead on on instaling but as to FQDN I am confused a little. I have a registered domain currently hosted on a paid vps that I plan on moving to my new server next week. Its been fully operational for a year. I have been reading about the need to set up Virtualmin with a domain but Im worried mail set up is going to be a possible issue. I dont understand what I should use as the FQDN when I set up Virtualmin. My domain will initially be the ONLY domain on the server and I need to move all my mail accounts to the new server along with hosting the web page. I read something about using or but am confused as to how that is going to translate with mail set up. I dont want to do a bunch of un-needed work after the fact so I am asking specifically about my setup here. If someone can tell me what I should use for the FQDN during set up it would be really helpful. If I use in Virtualmin setup. Will I be able to host that domain as a virtual server and have mail automatically set up when I create the virtual web server or is there going to be some conflict as I have read might happen? I got that from here:

Please help! Thanks!

When virtualmin is being installed, it needs the FQDN of the server itself. NOT the FQDN of any of the virtual hosts that will be hosted on the system. Although, technically the machine could be and a hosted domain name in virtualmin could also be on the same IP. But that could get confusing with email and DNS if you ever had to move a domain.
I essentially started the same way. I eventually ended up calling the server itself and my virtualmin hosted domain

As far as timing, when you first install virtualmin, you will be connecting by direct IP since your DNS does not point to that server IP yet.
so you’ll connect to to set it all up. So that initial FQDN isnt critical as far as accessing the machine. Thus naming it what ever you want, like is fine. Once all is setup and DNS is changed to the new IP and has propagated, you’ll then be able to connect to