With VLANs available is there a reason to use Private-Ips anymore (or private IPs with a VLAN)?

Hello all,

I am a bit new to all of this server setup, and I'm looking into setting up a private connection between a few Linode servers. I am reading up on VLAN and it mentions in this doc

https://www.linode.com/docs/guides/getting-started-with-vlans/

that "VLANs are separate from Private IP Addresses. Private IPs are accessible to all Linodes in that same data center and can only be further restricted by firewall rules or additional internal configuration."

So I'm curious if there are specific use cases where one would want to use a Private IP vs a VLAN to connect between multiple Linodes? Is there a need to even Setup a "Private IP" when we have a VLAN already? It seems redundant. It also seems like VLANs are a replacement for "Private-Ips" but there are some limitations on VLANs, so Private Ips still might be needed in some cases it seems. I'm just not sure if they are ever needed to be used together, and why someone would do that when the VLAN itself is private?

Another snippet from that link

"Configuring the Network Interface

VLANs are managed within the network interfaces on a Linode. Each Linode has 3 configurable network interfaces, which are referred to as eth0, eth1, and eth2. The purpose of a network interface is to provide access to either the public internet or a VLAN:

Public Internet: Configuring a network interface for the Public Internet enables the public (and private) IP address(es) for that Linode. If no network interface is configured as Public Internet, the Linode will not be able to access the internet or other Linodes within the data center’s main private network.

VLAN: Configuring a network interface for a VLAN enables the Linode to communicate over a specified VLAN.

None: Selecting None will deactivate that network interface."

It also mentions here that if there is no public(or private) then there wont be internet access, or access to the "Main PRivate network" but with a VLAN you will be able to communicate just via that private VLAN, which seems to be what I am looking for.

Thanks for any help in understanding the differences between "Private-Ips" and "VLANs" and if there is any reason to use them together, or why would one want to use a Private-IP, if there is the ability to use VLANs(Both seem to only work via the same Data-center).