As we learned from Katakuri there are multiple levels (or tiers) to each type of Haki. Here is my personal belief of the tiers for each Haki type.
“Tier 1” and “Tier 2” are trainable while “Tier Unique” is only for those with strong Haki by birth. The “Tier Unique” is also a passive haki ability although it requires a certain amount of Haki to be used. I think of it like Mana points but for Haki.
Tier1: Heightened instincts
Tier2: Future sight
Tier Unique: Ability to hear the Voice of All Things
Tier1: Hardening physical things (body or objects)
Tier2: Katakuri leads us to believe it even harder haki but i don’t agree. I’m not sure what it could be but I’d like it to be manifestation of Haki (making things from Armament Haki)
Tier Unique: An invisible indestructible shield around your body. Big Mom being the example for this tier.
Tier1: Knock out people with weaker Haki
Tier2: Inflict physical damage to object and people
Tier Unique: Control over nature. This is seen from when Whitebeard and Shanks clashed and the weather began to change.
*Theory by Cavenfish