/usr/local/lib/node_modules is the correct directory for globally installed node modules.
/usr/local/share/npm/lib/node_modules makes no sense to me. One issue here is that you’re confused because there are two directories called node_modules:
/usr/local/lib/node_modules
/usr/local/lib/node_modules/npm/node_modules
The latter seems to be node modules that came with Node, e.g., lodash, when the former is Node modules that I installed using npm.