This bit is useful on horses that tend to lean or snatch down, the lozenge disperses pressure across the tongue, relieving unwanted pressure from the edges of the tongue and the palate.
Generally the thicker the mouthpiece the milder the bit. A horse with a large tongue or low palate might be uncomfortable in a bit with a thick mouthpiece.
The two rein options will allow the rider to have varying degrees of control being able to differentiate between the snaffle rein and the running cheek rein that provides poll pressure. Use either in conjunction with rolled leather cheeks, aesthetically pleasing and softer in their action, or rope cheeks that have a faster action.