Upgrading the stock wheel would be worth it only if the value brought by the substitute wheel, in terms of aerodynamics performance and weight, is significantly higher than the cost or if the stock...
One can say that TT Tri Bike is noticeably faster as they are more focused on aerodynamics. But there are some times and places where a road biker can be competitive.
Racing a triathlon can be a fun activity if you know what you are doing. You should have proper knowledge of what to eat and when to eat that. Do you start eating just after the race? Do you wait and...