Do I need to enable Dev Hub in my PROD Org?

Dev Hub can be enabled in Developer Edition orgs, but the scratch org limits are significantly lower than in paid Salesforce production orgs. In a Developer Edition org, the limits are just 3 active and 6 daily scratch orgs, which might suffice for an individual developer who is not using continuous integration but can be stifling in a process that likes to use a lot of orgs. It's not feasible to share a Developer Edition Dev Hub across a team; each developer would need their own.

Production orgs, as described in the linked documentation, offer an order of magnitude more scratch orgs. To use Dev Hub in production, you can request special free, limited access licenses (I wasn't sure if that's what you were alluding to in your question) to enable developers to authenticate and create scratch orgs against Prod, without viewing CRM data.

Of course, some organizations may be unwilling for compliance or process reasons even to use those licenses, in which case you don't have much recourse other than a separate paid org or multiple Developer Editions.

So I need to know if having a Dev Hub org that is not my Prod org is ok.

Typically it should be OK. However you will end up having limited number of Scratch Orgs that you can create using a DE Org.

The Enable Dev Hub in Your Org documentation lists down all such considerations while using a trial or DE Org as Dev Hub. One of the key considerations out there is as below, so you should plan your implementation approach depending on the scenario.

If you plan to create package versions or run continuous integration jobs, it’s better to use a production or business org as your Dev Hub because of higher scratch org and package version limits. Package versions are associated with your Dev Hub org. When a trial or Developer Edition org expires, you lose access to the package versions.