Ask HN: How Does Appodeal (Programmatic Ad Mediation) Work?

I put ad banners in mobile apps and I use Admob mediation to show ad from Admob, inmobi, Mopub, MMedia. Recently I heard Appodeal which describes itself as the programmatic ad mediation. I read the official Q&A: Appodeal’s Programmatic Mobile Ad Mediation Approach http://blog.appodeal.com/qa-appodeals-programmatic-mobile-ad-mediation-approach/ but still don't know how it works. The key things I found about Appodeal are:

1. Appodeal claims to choose ads with highest eCPM from Admob, Liverail, Applovin, Mopub, Avocarrot, UnityAds, etc.

2. The ad revenue from Admob will be paid to the app developer directly by Admob (Before you integrate Appodeal into the app, you have to own the Admob account and link it to Appodeal.). Ad revenue from other ad networks will be paid by Appodeal. You don't even need any account of these ad networks.

For #1, I don't know how Appodeal achieves it. As far as I know, in admob/inmobi/mopub's SDK, there is no option for me to set eCPM floor.

For #2, I don't know how ad revenue from other ad networks goes into Appodeal. When I use mopub, I need to have a mopub account, input payment info, add apps in the mopub web console, integrate mopub sdk and use the ad unit id in my app. Mopub will pay me. But with Appodeal, the app developer doesn't need to do these steps. Revenue goes into Appodeal directly. My guessing is Appodeal reuses an ad unit ID for all customers' apps. (Probably it is not correct.)

My questions are:

How does Appodeal work?

Can we trust it? Because Appodeal gets the revenue first and then pays app developers, if it takes half of it, nobody knows.

Update:

There is another programmatic mediation platform called AdtoApp http://www.mobyaffiliates.com/blog/adtoapp-officially-launches-its-programmatic-mediation-platform-for-in-app-advertising/