When importing from MH 1.2 into Blender 2.91.0 with the MH 1.1.0 plug-in, the elbows and kneed bones are not connected. I'm using the GameEngine rig in MH.
Also foot isn't connected to the low leg bone.
In Pose Options, Auto IK seems to have no effect.
So, currently cannot find a workflow that works with MH and Blender.