Is it possible to implement a base ArcGIS Enterprise in the Amazon cloud and configure it with IWA in our internal network?
Did you see the separate documentation links?
Yes but I haven't seen any section talking about IWA in Cloud.
Azin ... They list what is supported, so if it isn't on the list, you should check with your rep and see if it is an omission or pending. That is about all you can do unless someone else hops in with a yea or nay