When I got into the hobby a couple years ago, I spent a lot of time reading and researching many different subjects. Couplers was one of the subjects. There is plenty to find for free on the Internet, and there is plenty in hobby publications too. What I found I needed to do was the following:
I put Kadees on ALL of my locos and rolling stock. On the cheapie cars that had truck mounted couplers, I ditched the trucks for new Atlas or Proto2000 trucks, and body-mounted the Kadee draft boxes.
On cars like Athearn and Accurail, I usually cut the factory draft boxes off and replace them with Kadee draft boxes. Sometimes I leave the factory draft boxes, but only if the Kadee couplers work perfectly in them.
I use the coupler height gauge to check everything and use a fiber washer between the truck and underframe if the coupler needs to be raised just a tiny bit. If the coupler needs to be raised significantly, I use a Kadee #47 coupler which is offset to be higher. If a car ends up with a coupler that is too high, then I place a shim between the underframe and the draft box.
To me, perfectly working couplers are an absolute must to enjoy this hobby, especially if your layout is an "operations oriented" layout where you will be constantly switching cars, coupling and uncoupling them. It pays to spend a significant amount of time and money making everything RIGHT.
