CPanel DNSonly Configuration

I have some question regards configuring a cPanel DNSonly
server. What I have done so far is that I have a VPS in an other DC, in an other country then were my servers are. cPanel DNSonly is installed and right now I am wondering have I done it all in a proper/correct way and how can I test it to see if it will work without bringing server down of course :-)

I made all servers in the cluster on the DNSonly server the DNS role to Standalone, is that ok, and if not why???
Will the DNSonly server then operate as the backup? On the dedicated server side I added it in the cluster and told it to synchronise changes. So I assume the dedicated server will send changes to the DNSonly server, is that correct?

If I make all servers on the DNSonly (VPS) instead of Standalone to status: Synchronize changes, will all servers get from each other as will in that cluster all the zonefiles?

Sorry, I am a bit in the dark with this :-)

Can I change the second name server on each dedicated server to point to the main IP of the DNSonly server? the VPS main IP.

What can I do to test it for correct working?

Is it a good thing to have a second VPs geographic other side of world to do the same with, will that help in more reliable dns and even faster to find websites for my customers?

The latest cPanel DNSonly version doesn't allow me to view the CSF firewall to display, It is working, but nothing to configure from the WHM, I can of course set the firewall specific rules, but one of the VPS hosters recommend to run without firewall as he said nothing to be worried about? Any advice in this? is that true?

is cPanel DNSonly a good solution for a redundant DNS? Are there any other easier options for a cPanel/WHM based config?