Lachgas means laughing gas: nitrous oxide, N2O. It comes to a kitchen in two shapes, and choosing between them is about how you work rather than what the gas is.
A cream charger is a sealed unit at 666 g, 2 kg or 4.33 kg. It goes onto compatible dispensing equipment, gets used, gets replaced. Nothing about storing it or keeping a spare is complicated.
A professional tank at 5 kg or 10 kg is a cylinder instead. Much more inside, a compatible regulator required, and a proper place needed to keep it. The benefit is that service does not stop to change a unit.
Which one depends on volume. A pastry bench plating to order does not need a tank. A hotel kitchen running foams across three services generally does. Between those two, ask how often a change gets in the way.
The rules are the same either way. Both are supplied for lawful culinary and food-service use, with equipment listed as compatible in the current manufacturer instructions, inside the regulations that apply. Inspect before use, never run damaged or wrongly connected kit, and follow the manufacturer on ventilation, storage and disposal.
Not sure which suits your bench? Tell us the regulator or siphon you already run and we will check it against the listing.