network config

Centos 7.4
Webmin version 1.881
Usermin version 1.741
Virtualmin version 6.03 Pro
Network Interface enp5s0f1

I was given usable external IP range
69.197.145.146 - 69.197.145.150

I feel stupid about this cause it’s just not clicking in my head so correct me if I’m wrong. The Net Interface is working just fine.
If I add a virtual interface, it’s only an internal interface and not actually using the external ip address?
And under the Host Addresses, if I have say s1.domain.tld as 69.197.145.146 with rDNS pointing 146.145.197.69.in-addr.arpa -> s1.domain.tld, could I add s1.domain.org then have it use a different ip address or am I overthinking it and my idea needs another physical nic card?

You’re over thinking it.
enp5s0f1 can be your main interface on what ever IP you want. Your example is 69.197.145.146.
Then add virtual interfaces for the remaining IPs. enp5s0f1-1, enp5s0f1-2, etc.
Those virtual interface will see the outside world as if they where a physical interface.
Yes, you can have your .tld on 146, then .org on virtual net ip 147, and as many domains as you want can be assigned to any ip available.