No changes will be made to your account, characters, progression, or inventory, your platform, game data and entitlements, wallet balances, and access to the games. What’s changing is customer support providers and the Terms of Service.
Lost Ark’s new publisher warns that it will not transfer in-game mail, friends list memos and group names, blacklist memos, guild member nicknames and memos, stronghold gift messages and quiz data, chat messages and chat history.
But all your preset names (gear, gem, skin, skill, etc.), ship names, stronghold slot/playlist names, map and combat memos, chat macros, NPC renames, and game progression data will be saved.
If you don’t want your data transferred, you can opt out in both games.