I don't have the Regulator, but own several other RR products. It is made from the same material as their other shirts, so it is not going to work as a windshirt. Zipping the side vents might be of some value. But for me, if I need to zip the sides, then I am wearing a BPL Merino Hoody not a RR shirt. A wind shirt needs to be a separate item, IMO.
Another great product RR sells is the Eco Speed T. I wear this a lot. I really hot weather with little water availability, I wear an Adventure shirt to reduce evaporation from my torso. If there is plenty of water, I wear the Eco Speed T. I am not concerned with UPF protection because I have a dark complexion.
With the Eco Mesh pants, I rarely zip up the sides, unless I am in heavy brush. The mesh panels get caught on branches and such. Good think is the mesh does not rip, but it will snag.
Another shirt by RR I like is the Madison River. Similar construction as the Adventure shirt, but it has a collar and several pockets. It also has a zipper pocket behind the left front pocket. Good shirt for long day hikes when I may not carry much of a pack.