Well, lots of ways to go these days. The "war belt" has morphed into almost an EDC belt, so a lot depends if you plan on using it for every day carry, or is it strictly for overt carry/range work.
In regards to the two-belt system, basically you have an inner pants belt, which can be worn stand-alone if you like. It will either have a low profile buckle, or none at all; simply using Velcro for closure. This belt will typically have some loop Velcro sewn on the outside of it. Some belts use the classic police "keepers", which are just loops of webbing (normally 4), which also bind both belts together. Either way, your "war belt" is now anchored to your pants belt, so it won't sag or move around (well, as long as you are wearing pants that fit you, pulled up in the normal position around your waist, with the belt cinched up snug). This is a good system because it supports the weight of pistol gear without the use of suspenders. It gives you some versatility because you can take the war belt on and off without having to thread it in and out of your belt loops. Good for classes and training. Also good as a first responder rig.
A note: Some mfg's use 2" inner belts on their designs. I think this is not optimal. I use 1 1/2" webbing because it will fit the belt loops of most modern pants these days. Unless you have some mongo tactical trousers, you may find 2" a bit much. So I would look for a system with both inner and outer belts at 1 1/2" width. 1 3/4" might work with some/most pants, but I like 1 1/2" mo better. I also like the 1" cobra buckle as a closure on the outer or war belt. It matches the width of the 1 1/2" webbing much better for every day wear or just comfort whenever you have it on. Unless you are from Texas and have a big rodeo prize buckle already; then never mind.
Now another option. If you don't want to tie both belts together, you can kick it old school ranger style with suspenders. With a good set of suspenders, that have some stretch built in, you can "float" the warbelt on your waist, letting it raise and fall, as you maneuver. Look at pics of Pat Mac for a good example of this technique. You typically wear the belt slightly looser, so it can level out as you kneel, squat, whatever (but with a handgun, you might snug it up more and use the shock cord for stretch). This might be an issue for some, depending on your build. The pistol can shift position somewhat, as this was a classic rifle patrolling rig before wearing handguns became de regueur. But it's still a valid technique if you set it up properly. This was usually done with the larger, padded belts, which have fallen out of favor with some.
A word on width. This is a rapidly moving target as new designs seem to come out daily. I like a 1 1/2" width, but there are also 1 3/4", and 2", 3", and 4" designs. It all depends on if you want some kind of "molle" system on there for pouch attachment, which calls for the wider belts (usually 3"-4"), or if you are going to use dedicated belt pouches in either nylon or kydex (or both). They all have their plusses and minuses; it really depends on you and how you plan to use it.