I personally would consider Tolkien (the books in this case) as low fantasy, despite the epic scale and elves/dwarves. As well as the Witcher.
High fantasy would be something like D&D where you have bikini armors, flying castles and magic portals.
A lot of this has to do with the visual design of the world and its assets and the overall atmosphere. It all depends on how you implement it, not what you implement.