Do different types of the kadee, or { similar types of couplers } work and connect with each other? Thanks, for any helpful posts and info.
All Kadee couplers will work with each other and most of the knock-offs. They won’t work with Sergents couplers unless one is pushed down into the other.
Sideways works too on Kadee and knockoffs. If the knuckle face is thin enough, you can open the Sergent and push the couplers to the side until the Sergent curves over and locks itself with the Kadee inside. It’ll also work on Horn Hook couplers.
And, just to clear the next hurdle, Kadee & Horn Hooks couple solidly as well. I have not figured out how to mate a Kadee and a Euroopean hook-and-loop yet. 
The short answer is, yes, Kadee and the knockoffs (Bachmann’s EZ-Mate, McHenry, Walthers ProtoMAX, and others) all work the same way and are interchangeable. There are some significant quality differences between them, with the metal ones (Kadee, Walthers) being significantly better than the plastic ones.