I use mine mostly like a panini press for sandwiches. But, I have used it to cook meat.
I only did a steak on it once, and it did make a considerable amount of smoke. Burgers smoke, too, but they cook pretty fast. The smoke is about the same as pan frying the same meat.
I have done bone-in, thick pork chops, and they worked just fine, although I still prefer other methods, such as sous vide and sear. The Griddler would probably work well for the sear part, if you turn it up to high. The bone didn't seem to cause any problem.
I have never used mine "open," like a griddle. I can do the same thing with a skillet.
As for fish, I have never tried cooking it on the Griddler. There again, I prefer to sous vide and sear, or pan sauté my fish, which is usually a delicate fish, like cod. I can see possibilities for a meatier fish working well on the Griddler. Perhaps a tuna steak you want to sear and leave rare inside. You could do that with the Griddler closed.
BTW, the Griddler makes outstanding pressed sandwiches, like paninis and grilled cheese. I make a killer Cuban on it (see below). Oh, quesadillas too!
“People say nothing is impossible, but I do nothing every day.” Winnie-the-Pooh