PFF's is probably the most realistic, but, for that very reason, I find myself often getting stiffed for the better players. Blah.
This one's my favorite. It's a good blend of reality and fun.
https://www.nflmockdraftdatabase.com/mock-draft-simulator
I've never done one of these - so I gave it a shot. What fun! I can't believe all the trade requests....I ended up with 5 or 6 second rounder. (I never met a trade I didn't like).