TC-W3 is the rating, and you want to use an oil with that rating or higher. 2W is Yamaha's designation for oil they recommend for wave-runners with catalytic converters. 2W is also recommended for use when you are running engines where the throttle is being varied (like on a PWC). 2M oil is designed for 2 stroke outboards. It works better in engines like outboards where there is not as much throttle variability (basically running at speed like in a boat). Now that you have gotten rid of the cat. you could use other oils like the 2M, but you may loose some top speed and throttle response. Bottom line if you want the best performance, even with the D-plate, then stay with Yamaha's 2W oil.
There are other brands of TC-W3 oils on the market, but I'd check to see if they say they are recommended for a PWC before using one.