Usually, they're both pronounced with a long "ee" sound. In some cases, the single "i" is pronounced short. For example, Alduin would normally be pronounced like "al-doo-een", but a lot of times it's pronounced like "al-doo-in". There isn't a rule about when "i" should be pronounced short or long, it's just how different voice actors pronounced their lines in the game.

By contrast, "ii" is always pronounced with a long "ee" sound. Dovahkiin would never be pronounced like "doe-va-kin". Hopefully this all makes sense!

When you see "ii" in a word, that's usually the stressed syllable. Other than that, you're right. It usually comes down to individual pronounciation. A common word in Dovahzul is "Hi" which means "you." Some people say it like "high," while others, myself included, say it like "hee."

oh so its really just up to the person on how to pronouce "i" at certain times?