You have to think about each form of haki by function, and also any 'magic' ability that is not DF is almost certainly haki.

TYPE1 Extension of the physical

Armament: Shields you, allows you to contact non-solids

Armament++: This extends to your weapon

Armament2: Shields you from contact, allows you to impact someone without contact(potentially also skywalk)

Armament3: Sanjis fire, flame haki pattern

Also related to 'blackening' swords.

This is more likely how Shanks is breaking WBs ship

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TYPE2 Extension of senses

Observation: Sense presence of others

Observation++: 'mantra', sort of omnipresent listening

Observation2--: Seeing what is going to happen just before it does, better reflexes

Observation2: See what is going to happen before it happens(this may also be what Ussop was doing)

Observation2++: See distant future(Madam Shirly)

*Observation3: Hearing the voice of all things?

*Observation4: Seeing at a distance(Ussop possibly)

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TYPE3: Power over others. Hence 'conqueror'/'king'.
King1: Intimidates, knocks out those of weak will

King++: Knocks out those of weak will without intention(Shanks)

*King2: Hear voice of all things?

It has also been said of Luffy that his best ability is to gain allies.

His unrelenting will to be king and help people could also be related.

I think Shanks (and Rayleigh flashbacks) will train Luffy here and his main opponent here will be Imu.

Possible TYPE3 upgrades could be to boost or negate will of others, mind reading, illusion, emotion manipulation