5w and 10w should be readily available from most electronics stores, larger wattage ones(50-250w) I've only seen in 4 and 8ohm versions,mainly used for testing audio amplifiers.
in this case 10x 2ohm 5w or 5x 1ohm 10w *is* the simple and easy option
oh paralell is splitting the "electron flow" so it goes through all the resistors at the same time, not in a long line.