Hi - I own a 20 gauge SLX600 Black. To answer your questions - they have inertia triggers, not mechanical, lock up is by a lower lug into the monobloc similar to a browning, as opposed to a beretta double pin design.
Overall it is a very nice gun, finish is very much like a Silver Pigeon, decent walnut, nice bluing, and the gold engraving sets it off nicely. Very attractive and others have commented on the appearance. Mine was very stiff to open when new, and I spent a couple of hours working the action to help loosen it up. After about 1000 rounds it started to open easier, but it is still a little hard. What that tells me is that the tolerances are tight and the gun is well made. Took the stock off and the trigger mechanism is nicely machined with no burrs or crap floating around. Lockup is solid.
How does it shoot - very well with balance just in front of the hinge, decent triggers, standard ergonomics but it is pretty light at a little over six pounds to be used as a sporting clays gun even in 20 gauge, which is what I shoot. It would be a great hunting gun - which is what FAIR seems to favor even though they make a few dedicated target models, their catalogue seems to be more hunting oriented.
At a price point $500-700 less than a Silver Pigeon I think it is a very good buy. Much better than the top of the line CZ or Tristar. Other than the stiffness when new, I have not had a single problem in 5000 rounds. It looks nice, is well made, seems to be reliable and as a hunting gun I would not hesitate to recommend it.