Pretty self explanatory, It would be great to have this kind of option for maps that are not necessarily has the sea level at y64

you can change the spawn height in the config. is that not sufficient?

Not really sadly, using ground fog at any Y level would help drastically visuals wise. cuz like ground fog isn't something that is also static in real life either, it can happen at any height. Tracking the player would be a solution albeit bit dirty (ability to add biomes to the config and specify the spawn level would be a cleaner solution)