I figured out how to tell the difference between bots and real players pre lobby screen. Bots will do emotes and you cant mimic them. You can only mimic real players emotes.
BOT RUN 2.0 - Fortnite Creative Map Code - Dropnite
Fortnite: Chapter 2 - Use This Simple Trick To Get Bots-Only Matches | Bot Match Guide - Gameranx