When you attack in Legend League, you do not raid resources from your target. Similarly, you don't lose resources in attacks against your village.
The amount of loot on offer is determined by your target's Town Hall level, as well as the strength of the village's defenses. The stronger the village, the more loot is on offer as a reward. Your own Town Hall level does not affect the amount of loot on offer.
Raided resources are added to your storages immediately after battle. They do not overflow your storages.
Raided resources are also added to your Season Bank.
Attacks in Legend League also reward the Loot Bonus and collect stars towards the Star Bonus.