The weight from the battery pack puts this truck into 1-ton gas pickup territory in terms of curb weight. That's why it can tow 14,000 lbs. They went with 8-lug axles and that was the only thing holding the 1500 series trucks back. The laws of physics are always present. I'm quite certain that this truck will easily tow to its rated capacity, especially since all automakers are on board now with SAE J2807.
As mentioned the only question is how far can you tow a trailer before you have to start searching for a charge station? If we look at the F-150 with extended range battery, we've seen those getting around 100 miles of range while towing in the real world. BUT, most people are going to need to leave a reserve in the battery because you don't always have a charge station in-line with your route. So let's say effectively you've got 75 miles between stops. RAM is claiming 180 more miles of range when unloaded, so if we do the math maybe we're at 60 miles of towing range over the Ford. So you're still having to stop every 135ish miles or so. Probably won't be a big deal for local jobs, but people driving long trips on vacations are not going to want to put up with that.