8 days registration deadline

8 days is the default Schengen rule.

That means within 8 days of arrival you should apply to register.

In practice most big municipalities and the ones with a high number of expats tend to have long waiting lists to get an appointment. I should not worry. Id does not hurt you you sent them an email or call them. Sometimes it happens that people might cancel an appointment and you can take an earlier date.

Regarding for the where to live, it does not really matter, you can even live in the other side of the country it is still fine.