Can I wear an endurance jersey for racing?

Yes, but you will have a small aerodynamic disadvantage compared to a race-fit jersey. At speeds above 35 km/h, the looser fit creates slightly more drag (roughly 5–15W depending on the jersey and rider). For most amateur races, this penalty is less significant than fitness and tactics. If you race competitively at a high level, a dedicated race jersey is worth the investment.