Q. When is it useful to enable pool tagging?
A. Pool tagging is enabled by default. In case you suspect certain drivers corrupting pools you should enable Special Pool in Driver Verifier. Here I refer you to Windows Internals, 5th edition, pages 799 – 801 for details.
Q. Can you give some basics on how to get more information about “resources” (like returned by !locks command) or even synchronization event objects shown by !process.
A. Unfortunately events are very difficult to analyze as they do not have owners as critical sections, mutants and executive resources (!locks). Here's one example with events as terminating wait chains: