Trying to set expectations for room upgrades across Marriott’s hotels. I am a gold elite member and i have never recieved room upgrade in my last three trips in 5 hotels. So wondering

• How significant is the difference in complimentary upgrade success between Platinum Elite and Gold Elite?
  
• Is it effective to request an upgrade before arrival (via app, chat, or email), or is it almost always decided at check-in?
  
• Any other tips or data points on maximizing upgrade chances?
  

Appreciate the insight.