I'm pretty sure they will try to follow the 5e Dungeon Master guide which list a lots of pre-existing generic and unique items, explain how to create new ones (either as a designer or via crafting) and even provide loot tables.
BG1/BG2 items are from AD&D manuals. The Holy Avenger, the Flame Tongue, Boot of Elvenkind, etc. Enemies gold/gems drop were also based on D&D loot tables too.
In other word, Larian just has to follow the D&D manuals.
