Panharmonicon will not double the divinity counters on any of the Myojins because the ability that adds a divinity counter is not a triggered ability. Myojin of the Seeing Winds' ability says
Myojin of Seeing Winds enters the battlefield with a divinity counter on it if you cast it from your hand.
This is a static ability that creates a replacement effect of the type described in rule 614.1d that modifies how the creature enters the battlefield.
No, you will not get an extra counter.
603.1. Triggered abilities have a trigger condition and an effect. They are written as “[When/Whenever/At] [trigger condition or event], [effect]. [Instructions (if any).]”
If an ability does not start with "when" or "whenever" or "at", then it is not a triggered ability.
Note that certain abilities, like Saga abilities, have the word "when" in the rules text; not written on the card.
Easier way to explain it is, look at Dark Depths, the wording on it is:
Dark Depths enters the battlefield with ten ice counters on it.
And it triggers "When it has no counters". If the first part was a triggered ability and triggered when it entered the battlefield, then Dark Depths would enter the battlefield with no counters on it, the trigger would go on the stack (and panharmonicon would make it trigger an additional time if it was a creature or artifact (let's pretend it applies to lands for the sake of the explanation), panharmonicon would make it get an additional 10 ice counters on it which would also go on the stack, the game would then check that it in fact has no counters, so the transformation ability of it would go on the stack, making it so that dark depths would be simply a 0 mana 20/20 indestructible.
The wording on Myojin, which is the same as the one in dark depths is not a "When it enters", meaning, it doesn't check if it can resolve on entering, the wording is "it enters with(...)", meaning the card already comes into play with it and doesn't gain it when it enters.