You don't need a VPN when you use tor. In fact, it's probably less secure since it's going through a private server that might have a government black box hooked up. Also, no FBI or CIA agent is ever gonna tell you to use tor???
The people who have been caught on tor doing illegal stuff just had poor op sec. I think pompompurin (former owner of breach forums) got caught because he used a personal email talking to someone lol.
The guy who created the Silk Road got caught because he recycled the same usernames for different accounts, one of which could be traced back to his identity
Also, he logged in via a library's public wifi
I just watched a YouTube video about that last week