I built a cap out of stainless steel to cover the fill stack on my LSG Mini. However, I have a TIG welder so that wasn't much of a project. You can get stainless material from McMaster Carr on-line if you don't have a local source. It's a flat plate cut slightly larger than the stack with three small tabs to hold it from being knocked off.
Texas 2.5 has a video on his YT channel with a fully loaded mini. I believe Fatt-E's BBQ has a large fully loaded for comparison.
Re: cooking with water. I cooked with water my first 30 or so cooks on my IVS as suggested by the product literature. Cleaning up the water pan(see grease & water) after the cook was always a huge pain in the ass since I live in an area where I can't just dump it without consideration. Finally tried it with just a foiled water pan for easy clean up. No big difference in the quality of meat between with and without water. Unless I find a need to use water in the future I'm going to avoid it for ease of clean up.
Nice looking smoker choices. I struggled with my IVS choice early on. The good news is you'll probably be happy with any of the smokers you quoted. The bad news is you have to choose & live with it(unless you're rich!). Can't comment on any of them, but I did eye ball the LSG Mini for quite some time before biting on my Humphreys. Do I have buyers remorse for not purchasing the Mini? A bit. Am I happy with the Battle Box? Damn right I am!
The biggest difference makers, other than the obvious materials & overall size of the IVS products, were the small things like door hinge quality, latch quality, wheel quality, etc. Some groups cheap out on small items that might end up having to be replaced sooner rather than later (see: 270 smokers).
