I confirm certain answers to your questions, there is a circular revenue agency that I suggest you to download from the site of the same on the way of declaring accounts abroad.
In point 1 of your exact question you must by law declare on your declaration (only framework rw) if you exceed the limit.
In point 2 of your exact question you must by law declare accounts that exceed the limit, for the payment imposed.
Now let's go on the modalities, it is certain that the Bunq bank communicates to the Italian state the average stock every year for the fiscal transparency and anti-money laundering regulations. So we must declare it, the beauty is that they do not start the movements of the same, if not after a specific investigation of the Italian tax authorities! This already greatly improves the fact that the tax authorities cannot "see" what moves on your account.
For the 25th issue of iban , considering an iban an account, you must declare all those who exceed the limits ... Council pay attention to the thresholds!