The Model 3 is an official clone console if that makes sense. It was licensed by Sega, but produced by a 3rd party, and even had its own 6 button controller complete with autofire options. It works with the 1st party 3/6 button controllers. It lacks the ability to work with the add on consoles like the Sega CD, but is region free, meaning you play foreign carts with it. It's very light and doesn't take up much space. I have either 2 or 3 of them, and they work great for tournaments. My major complaint is that due to their lack of weight, they are prone to moving.
I run the Edge of 94 Midwest annual tournament. We use all 3 models of Genesis, with CRT displays, but use Analogue's Mega SG FPGA console for the main stream setup, which plays in glorious HD with no scaling lag.
I'm not aware of any relevant tournaments using emulators for local tournament play, but obviously that's how the community does online leagues and tournaments.