Dear Erica,
I regret to tell you that I'm not a gaelic speaker and so I cannot answer your first question with anything that would come anywhere near confidence. I would guess, though, that the first phrase quoted by you might be a more accurate representation of the way in which Robert II, King of Scots, might have been addressed by one of his gaelic speaking subjects than is the second. I would need to investigate this possibility, though, before I would feel confident about giving an opinion. According to my understanding of this language, the gaelic words: "Ard Righ" mean High King, or more accurately, perhaps, High Chief. This leads me to suppose that the Gaels of olden times might have regarded the King of Scots as the Chief of Chiefs, rather than as king of the land which belonged to them, the Scots.
Similarly, I cannot say what the language of the Scottish Court actually was at this period, but the surviving records of government are either in Latin, or English. It does not follow from this that a gaelic title should not be used in the Geni-profile of this king but I'm not sure what his English speaking subjects would have made of it?
With regard to the use of long titles in Geni-profiles, can I make you aware of this important fact. Scotland has never been a gaelic speaking country. It is true of course that in the time of Robert II, King of Scots, many of the inhabitants of Scotland did speak gaelic but I would guess that a great many more, the majority, perhaps, spoke English.
I hope that this opinion is of help.
Kind Regards,
Neil