Hello,
I am by no means an Appodeal expert. I am in the USA I've been using it for several days while I'm developing. I seem to get a 100% fill rate. I am mainly interested in banners, but I have tried the interstitial and video. They work and are incredibly easy to use with B4A.
Appodeal works in conjunction with Admob. They do say you need to have an Admob account.
My guess is that this should not prevent you from using third-party stores. As far as I know Admob is part of Google but is not dependent on Google Play.
I have not published an app that uses Appodeal yet. It will be interesting to find out how it really performs. Compared to ad platforms I have used in the past, integration is so easy, I feel it is worth a try.
Barry.