A fume extraction MIG torch operates, on the welding side, no different from any other MIG welding torch. They use the same components (consumables, wire, cable, etc.) the only difference is that a fume extraction torch has a housing built-in, around those original components, and a front-end opening that we call a ''shroud'' to extract welding fumes directly at the source. Additionally, there is a larger diameter hose that surrounds the torch cable as a conduit for the smoke to travel to the vacuum unit/system where the smoke is filtered and expelled.
The general functioning principle of a fume extraction MIG torch is to extract the maximum amount of welding fumes possible, without affecting the weld puddle. If the vacuum pressure of the fume extraction torch is too high, you run the risk of extracting your shielding gas, which can lead to porosity in your weld. Start with the same parameters that you normally use and adjust the vacuum pressure around those parameters.