Use standard .NET. 

Normally you will build a repository type of class that handles the external communication. Use that repository class from page controller. Extend the view model with the type of data you want to display. Modify view to display it etc.. 

If you have a lot of business rules, add a service layer. Sounds like you don't need one if you are mainly displaying data. 

So standard .NET and MVC basically. Cache what can be cached...

Thanks for the reply! Yes, mainly, I will simply request and present data. The plan is to refactor most, or all, coding complexity down into Oracle/PLSQL, so that the API will serve nearly ready-to-present reports. This way, it's mostly a matter of just "decorating" the data as HTML. Initially, I thought if I am to use a Javascript front-end framework (eg Angular), I might just have access the API directly in Javascript, but maybe this is not the best way to go about this (in an Episerver context)? 

For just showing it's normally fine with a js solution. I normally go server side though. More options for caching, combining from multiple sources, logging, export to excel etc.