What EM/PM Should do and should not do

I've recently had more conflicts with the Engineering Manager in my team. This EM tends to want to influence the specifications of the product, even its design style. While I think having opinions is good, it's often hard to convince him. An important principle I believe in is "do not step outside one's role." I do not interfere with the details of their implementation, such as the database schema, API design, or even choices of system databases and infrastructure design. I use my technical skills to help drive the product forward. This kind of EM, or rather, this kind of engineer is quite common. They feel that having learned computer science, they assume designing or product management is relatively simple and want to get involved. This is a very unqualified situation. It also creates a challenge for PMs who don't have technical skills to counter such behavior. "Do not step outside one's role." Do not be a PM who interferes with technical decisions, nor an EM who interferes with product design.