I doubt its an of the above - my experience is as follows
Had this about 2 years ago. Prop shafts were balanced, replaced and re balanced to no avail
Diff bushes replaced - slight betterment
Paj spent near 3 weeks with Mitsubishi technical - they could not really find a problem at all
Tires changed - problems gone

- On tires, i have found the likes of Pirelli and Hankooks (softer type tires) make it worse, harder tires like the BFG make it better

Have your differential checked. My Gen 4 - 2008 has totally failed. Gears are fine, but the LHS bearing has collapsed. She still drives like a dream, albeit that she has around 13mm play in the side-shaft and the humming noise from over 100

This does not happen overnight and with daily use, this just gets worse n worse. (getting replacement diff n side-shaft on Monday

Further, this cannot be measured if the Paj is on the lift with its feet hanging in the air. She needs to stand on the tires on a lift - take her up_ and see if there is any vertical play in the side-shafts. In my experience, humming is from a failing bearing.