Before you get rid of your GMG have you thought about just putting a kitchen magnet over the fan air intake? This would limit the amount of air coming in and may solve your soot issue. Another thought it just to put some fire bricks around the cook chamber to build walls to keep the soot from flying out. Menards has 5 fire bricks for under $20.
I just got a Louisiana Grills LG700 and after some tinkering I have it within 20 degrees across the cooking surface.
It does have a cover over the drip pan you can slide open to grill directly under the flame but I don't use it (I have a gas powered sear station for hot and fast).
For reference these are the tweaks that I made to my LG700.
#1 - change the #9 setting on the controller from 100 to 250
#2 - when assembling the grill you want to make sure the auger is centered in the feed tube and tight.
I did this by putting 4 flat blade screwdrivers in the end to center the auger then put one washer between the feed tube and the motor mount on the RH screw, then tightened the LH screw.
#3 - These smokers have a lip under the lid that will accumulate grease - you want to put high temp silicone on the inside of that lip so the front of you're smoker doesn't get covered with grease.
#4 - Fire bricks - this made the biggest difference - place them around the fire pot to help direct heat upward for the first part of the cooker and restrict a little airflow to the RH side - it will take longer for the pit to get up to temp but temps will be steady.
#5 - I removed the hood thermometer and replaced it with a Tel-True
#6 - Just to make sure I didn't have any smoke leaking out of the lid I applied Lavalock high temp gasket around the lid and the hopper cover - I also added a clasp to pull the lid down tighter.
I'm like personalizing things so I couldn't help but mess with the grill after I got it - it may cook fine right out of the box but these are things that I did to try to get the most out of it.
The LG700 can be had for around $750 on Amazon, they also have a 900 and 1000 if you want more cooking space.