If I export only the posed mesh without armature, it looks smoother (as expected) than the posed mesh with armature.
I can describe what I’m doing exactly to reproduce the problem.
I’ve got a skeletal mesh, which has been exported / imported with the following settings:
Skeletal Mesh in Blender and UE4:
This is with the UE 4.22.3 Version. In the Dual Quaternion Version from the DAZ site (link given above) the distortion is even more pronounced / worse.
As for the rotation angles ue should deliver the same results as blender no matter how extreme the bone rotations may be.
Normally I’m using the Dual Quaternion Version + Corrective Shape keys for the armpits, so some poses may look wrong without preserve volume checked, but look good with preserve volume + shape key.