Planning on SharePoint support personnel fielding "how to" questions from SharePoint end users and site owners during a migration between versions of SharePoint server, on-premises, isn't a decision likely to deliver optimum returns.
SharePoint support personnel should have all the time they require to remedy "break /fix" issues - especially during a migration. Tasking the team with answering "how to" questions reduces the amount of time available to address truly pressing issues, should they arise.
A better decision is to plan on including an in-context help system (for example, an edition of our VisualSP Help System for SharePoint server, on-premises) in the migration. SharePoint end users and site owners can be notified of the availability of the system either via internal email, or an online meeting. Once they have been familiarized with the availability of the system, support personnel may have to handle some calls, but it will likely be a simple matter to re-acquaint users with the system already introduced.
We think the cost of acquiring an in-context SharePoint help system for end users and site owners is completely manageable. We offer an ROI calculator. Please feel free to use it as you require.