Yakisoba is 469 calories for what is really a fairly small plate, about 290g. The steamed noodle pack is 150g and roughly 300 calories on its own, then 30g of pork belly, cabbage, 5g of oil to fry it and 20g of sauce. At a festival stall you pay 500 to 600 yen for that. The sauce is only 25 calories, so it is not the villain here. The noodles are.
The festival version drifts higher. Stall cooks use more oil because the griddle is dry and hot, and they finish with a squeeze of mayonnaise. Mayo is 100 calories per tablespoon, so the 'mayo yakisoba' from a stall is about 570 to 600. Konbini yakisoba is around 500 to 550 for the standard tray and closer to 700 for the 'omori' double packs, with the number printed on the label.
Yakisoba pan is the same thing stuffed into a hot dog bun, and it is the classic 'carbs on carbs' snack. The bun is about 150 calories, so a yakisoba pan is 350 to 400 calories, which is not terrible for a snack but it has almost no protein, about 9g. If you are choosing between that and an onigiri with a boiled egg, take the onigiri and egg.