Class II (solid 1 1/4 square tube)max weight is 3500lbs, Class 3(2" square tube) is 7500lbs and class 4(also 2" square tube) is 10000lbs.
The ball size is dependent on the tongue it fits into, 2 1/8 or 2 1/2 would be common for the size of trailer you are looking at.
Air conditioning is nice as long as you have a generator or camp where you can plug the trailer in, otherwise it is useless.
Gas stove eliminates the need to draw on power, battery or land, for cooking and if you ever run out of power you can crack a vent and window and briefly use it for heat.
If the trailer comes with electric brakes and most do, you will need a controller. There are many designs but all do the same thing, I have a Tekonsha P3 and it is very handy as I have towed trailers of varying size and I can easily adjust how the controller works.
Hand cranks for the tongue are OK, they are not that hard to twist unless you have some injury preventing you from cranking it around.
Solor recharger is nice if you camp where you have to use battey power all the time but most end up buying a generator and recharge batteries that way, otherwise the solr will extend the use age time available before needing a full recharge, unless you get crazy with the Solar panels then it should be able to recharge the battery on a sunny day, but these systems are expensive.
Standard propane tanls are good enough for me, just make sure you fill them before a long trip.
Aluminum wheels are just cosmetic, your preference is all that matters here.
