Founder of a bicycle insurer here and I can tell you that the only way to deter people is by parking in secure private or public spaces (never, ever semi-public) and by making your bike less attractive than the one next to it.

2 locks is indeed the standard in big cities. Also make sure they are sold secure gold rated or Art 3. Anything else is a waste of money. There are a few new lock types which are supposed to work better against angle grinders like Tex-lock or LitLok.

Because the average bike price is going up it also becomes interesting to steal parts. A decent handlebar + shifters are easy to sell individually. Companys like Hexlox or Pinheads are working on locks to tackle that.