UE-5.1 has a issue with the First Person Template with either field of view, angle, or perspective. I have no idea how to fix, and verified it only exists on the 5.1 platform and not 5.0. I have made minor adjustments to scale/location/placement in retrospect to either arms, or camera on the FirstPerson Blueprint. These pictures are only using the template and no starting content.
I also ran into this issue and the only solution I found was to open up the FPS Template in 5.0 and a new FPS template in 5.1-5.3 and copy the location and rotation values (for mesh, camera, etc) from the old 5.0 Character Blueprint to the new one.