I think, in a manager should be mandatory the enough engineering knowledge to manage and set goals for the team, along with the soft-skills to keep the motivation and create engagement (one of the keys in a team-work) in all the members in that team. A lack in one of this sides could be a risk for the project.
Regarding the second question (Should they be able to do what you do so they appreciate what you do?), if they have a clear understanding about the work, effort and achievements of their team that should be enough to appreciate what the team does.
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