New to Panzer Campaigns, have many questions... Let's start with HQ's

[Xerxes77]

If broken and possibly isolated, would they offer any benefit or advantage to their subordinates?  Or would an HQ in such a situation be completely useless to it's subordinates as if it were completely eliminated?

These are great questions. Based on the information included in the manual I would say a broken and isolated HQ is as good as dead.

A trapped and broken HQ means its subordinate units will be deprived of all their HQ-related benefits (e.g., I believe they *won't* ever be able to recover from their Low Ammo status) for the rest of the scenario. Note that disruption recovery is still possible (if more difficult) depending on individual morale checks.

In practice the end result seems to be that keeping an enemy HQ alive in those conditions is preferable to destroying it. A gamey move maybe, but the idea is to prevent the deployment of a replacement HQ.