I just tested my 2500 on a ride including steep hills with 400 gallons of water (150 in trailer and 250 in bed). Not problem whatsoever. The difference is night and day. I’m glad I made the move.
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The Ram 8 speed ZF transmissions absolutely require fluid change. Ram says they are sealed lifetime systems, but that’s BS. The manufacturer says 80k miles. I actually am planning my second fluid change for this trans in the next day or twoand will gwt a blackstone fluid analysis completed like i do with every oil change. Honestly, going to start doing that with my pressure washer oil too.
I have 150k miles only my 2015 1500, which is lifted 6 inches running 37s. I tow full water on my 325 gallon buffer with 8 gpm hot pressure washer. Pushing around 7k tow load. Truck is heavily modified and tuned both engine and transmission, but they’re capable with maintenance. Sure, 2500 is better for the job, but not a requirement.
If you start to feel that kind of grab under acceleration and shifting, it’s either differential fluid or trans fluid needing to be changed, don’t ignore it. If it’s during a downshift for acceleration, probably the Trans fluid.
For changing the Trans fluid, oem filter is built into the pan, so best to buy aftermarket pan so you can change filter in the future, or add a pan with increased capacity. Dorman is reasonable. It’s cheaper and better. For fluid, don’t bother with the stupid overpriced mopar fluid. Valvoline maxlife is cheap, but thoroughly tested and approved for these transmissions. Its what I used on my first change and have ready for my second. Follow the directions below for the change procedure. Yes, follow all directions. This is to simply change the fluid and not flush the entire system. System flush is way more complex and those who want a full flush just drain and refill 3 times with running the vehicle for a bit inbetween each flush.
I have 12 years experience with these transmissions and have been a contributing member to several of the related vehicle enthusiast forums. Hope this helps, because you do need to properly maintain your 2500 now too. 
Edit: ignore the caution at the top. The valvoline fluid is an atf+4, but i don’t think when this trans was first developed that these fluids met specs or were tested to meet specs. That said, I can only confirm that the valvoline maxlife is the only atf+4 that I am confident that is compatible.
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