>  - how can one identify legit accounts of popular Nostr users? Right now I'm going based on highest follower count among the various impersonator accounts 

NIP-05. Also called Vanity Addresses. 

On my profile you see below my name mananguri@onlynostr.club.  That's a NIP-05 address.  Anyone can call themselves Mananguri, but only I have access to the mananguri@onlynostr.club registration PIN.

I can also use that NIP-05 address as my lightning wallet address too.  You just point the address to your own lightning wallet.  It's really simple to setup. Check it out.  

onlynostr.club 

 Thanks. I'm assuming that to add the NIP-05 address to your profile you have to prove ownership of the address?