The best Lansky source (and the best gangster bio ever, IMO) is "Little Man - Meyer Lansky and the Gangster Life" by Robert Lacey. Lansky was a violent thug when he was young, but operated behind the scenes later. He had plenty of allies, but didn't have an organization or a family per se.

One of the benefits of being a Don is that you can delegate your hits and other violence to your subordinates. Al Capone, although not a Don in the Mafia sense (the Chicago Outfit under Torrio and Capone wasn't a Mafia family) was nonetheless boss of a major crime family. After he became boss, he killed a man with his own hands who had slapped around Jake Guzik, his Chicago mentor and high-ranking member of his outfit. He also baseball-batted (but did not finish off) Anselmi, Scalise and Giunta (bodyguards, probably including Tony Accardo, finished the job). Albert A. probably was the most murderous of the Dons, and may have pulled a few triggers after he disposed of Vincent Mangano and took over his family.

No actual Mafia boss ever declared his real income because to do so would affirm his criminal activities. Columbo was a "real estate salesman," Gambino was a "labor consultant," Gotti was a "plumbing contractor," but the "legitimate" money they declared for tax purposes was a tiny fraction of their real income.