Re: Appsflyer remarketing
I am assuming that you are referring to Remarketing using Mobile app engagement campaign here. If that's the case, you will have to create separate lists for iOS and Android users. To create remarketing lists for both the platforms, process is different.
Here you can find more details on creating separate remarketing lists for both platforms and using Mobile app enagement campaign to retarget those users:- https://support.google.com/adwords/answer/6310675?hl=en&ref_topic=6363797
I hope this helps!