I don’t see much of a big difference between very frum MO people and more relaxed people from the yeshivishe world.
I only wear a black hat when I am davening in a place where it’s the norm. In my Modern Orthodox shul in Brooklyn, Sephardi shuls, Manhattan, Teaneck, Riverdale, I would never wear it.
In a black hat shul in Flatbush, Monsey, Baltimore, or 5 Towns, I definitely do wear it.