I wasn't thinking when I posted this that porch means different things to different people. This is to be an enclosed insulated addition (living space) to the existing structure. But built so that if/when the existing structure (mobile home) goes away an new building can be attached/built next to it.

The 2x purlins was simply to create insulation space with minimal thermal bridging. They would not be visible in the finished room.

The 10x10 post and beams were indeed just for aesthetics.