"What kind of father is Miikka?"
Translation:Millainen isä Miikka on?
I just made the same mistake(?).
Appearantly the information of Miikka is more important than his behaviour. You're stressing that you're talking about him. If you put the on before the name, you actually criticize or question Miikkas behaviour as a father. That is less neutral.
Did I explain this correctly?
If there is a question word (mikä, missä, miksi, millainen, kuka...), the word order stays the same (SVO). In English the word order changes (VSO - He is. - Is he?).
If the question is a yes/no question made using the -kO suffix, whichever word gets the suffix becomes the "question word" and thus comes first. For neutral questions, the word getting the -kO suffix is the verb. Using any other words emphasise that word.
Hekö ovat nyt naimisissa? (Are THEY now married?)
Nytkö he ovat naimisissa? (Are they NOW married?)
Naimisissako he ovat nyt? (Are they now MARRIED?)
Not really. I don't know anyone who calls their father "taatto". It's pretty archaic/poetic. If I heard anyone talking about "taatto" I would assume that they are talking about their grandfather and even then it's quite rare, "vaari", "ukki" or "pappa" being more common words meaning grandfather.