I hope someone more knowledgeable than I will have a happier answer to you.
From my testing I found that 1 is the maximum for health, temperature and wetness. Setting values higher than 1 did not increase the time I could be underwater. How do I know 1 is the max? I set my health to 0.5 and, in game, saw that the health meter was at 50%
Also, when not underwater, the air value is 1.
I didn't find any mention of speed or movement except for velocity which, since it is tied to player's location, I believe would only affect the moment the person first opened the game.