Hi! So, other ‘big’ places in Italy where the mafia is from (other than Sicily) are Calabria, Campania and Puglia.
While in Sicily, the mafia takes the name of Cosa Nostra,
- in Calabria it’s 'Ndrangheta
- in Campania it’s Camorra
- and in Puglia it’s Sacra Corona Unita
To be fair, those are only a few of the known groups. Other groups include Camorra barese (from the province of Bari in Puglia), the Basilischi in Basilicata, the banda della Magliana in Lazio, and the mala del Brenta in Veneto.
However, please do not be fooled by their origins, because as you can see in this map
the mafia is spread everywhere in Italy. The darker the color of the region, the more of their presence and activity 
Granted, there are some places where despite their heavy traffics, people don’t really realize their presence (Lombardy is one example). But, the main mafia groups are the ones I listed above, which then gradually expanded on the Italian territory (other than abroad).
Unfortunately I can’t help on this because I’m from Lombardy, therefore I’m not familiar with other regions languages and traditions etc.
I will say though that
regarding race, Italians are all white caucasians. You can refer to OP for help in character design. That obv changes with mixed people or second generation Italians. The biggest minorities in Italy are Balkans, Maghrebi + Egyptians, Middle Eastern people, central Africans, southern Americans and eastern Asians (especially Filipino and Chinese). Not sure if I forgot anyone 