EUS should be the first option if available since it is a senstive tool to evaluate small CBD stone and GB stone. It can also diagnose anomaly junction and pancreas divisum.
The indication to perform an ERCP in acute pancreatitis is that the patient have a high risk of choledocholithiasis (ASGE guidelines for choledocholithiasis and IAP APA Management Guidelines for acute Pancreatitis)
I do not think it is a good idea in a young healthy patient because of the risk of alithiasic colecistitis. I think that every young and healthy patient should undergo a colecistectomy after an ercp has Been