It will likely take you 10-20 min. to get to the Kona from the MK gates.
The monorail will be the most direct, as it let's you out steps from the Kona.
(But, often in the mornings, the monorails will "test the brakes" and/or "stop to let traffic clear."
The shuttle boat stops first at GF (unload/load other guests,) then motor over to the Poly, but the boat dock is a long walk from the Kona.
And, you want to be 5-15 min. early for your ADR.
So...