Separate the bus and rail jobs
The Seoul–Sokcho and Sokcho–Gangneung legs are road transfers in this route, while a later Gangneung–Seoul journey may use KORAIL. Do not put the bus spend into the eligible rail basket or buy a rail pass expecting it to cover Sokcho. Search each mode through its current official or authorised channel and keep the terminals visible in the itinerary.
Protect weather flexibility
A Seoraksan day is weather-sensitive and should not be squeezed between two fixed transfers. Give Sokcho enough time for a mountain day and a coast, market or weather-backup block. In Gangneung, group the lake, beach or coffee coast geographically rather than crossing the city repeatedly. Exact venue hours and trail conditions need a live check.
Book the constrained leg first
Once international travel and the city order are fixed, secure the intercity leg with the least useful alternatives, then choose cancellable accommodation near the correct terminal or local route. Keep one flexible activity after each arrival. Mobile data and Korean navigation apps matter more on this mixed-mode route, but device compatibility should be checked before buying an eSIM.