Yes the Nitto mud grapplers are loud, sounds like your in a B52 bomber. IDK about the trail grapplers. KM2s are a good on road/ off road tire. Out of the three you listed Nitto Mud grapplers will be the best off road tire, While the KM2 would be your best over all tire IMO.
Im currently running Swamper M16's. Out of all the tires I have ran I like these the best. Im surprised now quite they are on the road as they are a swamper. Off road they are awesome, second best tire ive ran off road.