Noob question - do I need to add a domain to my droplet for my site to show?

So, to preface, I already have 6 or 7 other sites all working just fine on my droplet. The basic setup:

1. Registrar points to Cloudflare
2. Cloudflare points to Digitalocean (two a records with droplet ip address)
3. On Digitalocean I have an ubuntu droplet with apache and multiple virtual hosts.
4. I also have each of the domains set up with Digitalocean. Each one has 3 NS records (ns1.digitalocean.com etc) and 1 A record (to the same ip address as on Cloudflare).

So, I was setting up a new site today and I’m really curious if step 4 is necessary?! I mean, isn’t the whole point of my using Cloudlare having the a records set up there? So I decided to try without step 4 and my site is still not showing (about 4 hours later). Perhaps this is just a timing thing and it will show shortly, but I’m now obviously wondering if it is necessary after all. Or does it take some time for Digitalocean to be able to connect calls from Cloudflare to the right virtual host?

Or is part of it necessary - for example the NS (perhaps that is how Digitalocean knows where to link that call from Cloudflare?).

I’m clearly a noob here, and I can always go back to what has worked in the past, but I’d REALLY like to understand what is happening here and if I can cut out a call it seems like a good thing in the long run.