Best Practise For Multiple IP Addresses ?

I have a VPS based on Centos 7 with Centos Web Panel. There are 4 IP addresses:

xx.xx.xx2.188
xx.xx.xx3.188
xx.xx.xx4.188
xx.xx.xx4.189

My server is installed on xx2.188 and I have set the shared IP as xx2.188

I have set ns1.server as xx4.188 and ns2.server as xx4.189

I have a number of client accounts set up on the panel spread over xx2.188, xx3.188 and xx4.188

And everything was going well. . .

Until I started messing around with the server and DNS nameserver zones. Having recently recovered access to the websites and email (a whole day wasted !), I wondered if I should change to the following:

• Leave main server address as xx.xxx.xx2.188
• Leave Nameservers as they are xx.xxx.xx4.188 / xx4.189
• Set Shared IP to xx.xxx.xx3.188
• Put all user accounts on IP address xx.xxx.xx3.188

What is best practise here ?
And what is the relevance of the Shared IP address if I can still access domains that are on other IP Addresses ?

Any enlightenment would be very much appreciated.

Kind regards

JC