Expo FB Audience Network Ad Mediation with IronSource / MAX-AppLovin

I am new here! I am using Expo and managed to show FB Audience Network Ad in Managed Workflow. But FB now require ad bidding so I need to add at least one more advertising network, preferably IronSource or MAX/AppLovin. But all the document only show React Native setup only. I am very confused on:

  1. Do I need to setup another ad network ad in my Expo App? Or the current FB ad should show the ad with highest bidding automatically?
  2. Does Expo even capable to include IronSource or MAX/AppLovin ad at all, preferably without ejecting? I saw there is a function FacebookAds.AdSettings.setMediationService(). Is it something for mediation? How does it work?
  3. And I just find that maybe can write some plug-in to resolve this kind of issues. Wonder if there are more details?

Please let me know any thoughts or example on how to make FB Ad mediation work in Expo. Many thanks!