Which hook to use for updates of all nodes of a particular type
I would like to know if there is a way to target only that node type directly from the hook and not to have the hook triggered for all nodes and then checking the node type.


Node hooks aren't that granular, they're invoked for all nodes and there isn't a system in place to make that selective based on the type. If you're worried about performance, don't be; the difference between the hook being invoked for all nodes, and a system to allow it to be selective would be negligible.

If you want to react to existing nodes being update, hook_node_update() is definitely the right choice.

You just need to test the type in that function:

function MYMODULE_node_update($node) {
  if (in_array($node-&gt;type, ['book', 'article', ...])) {
    // Do something.
  }
}