How to call local Oracle database ( on-premise) from PowerApps/SharePoint Online

we have SharePoint 2010 Foundation customized web parts build to retrieve data from on premises Oracle and SQL database. Since SharePoint 2010 will expired soon, we want to replace it by SharePoint Online for Office 365 and maintain function of retrieving data from on premises Oracle and SQL database. I am planning options for this replacement:  

PowerApps call Azure Web App API, Azure web App do Hybrid connection with the database (daily update); or Azure Web App API call SQL and Oracle web service, return OData collection.

At same time, I also think an option of SharePoint Online list using BCS, WCF to get external list, external content type return to SharePoint Online as SharePoint lists to get the on-premise data.

I am not sure which one is more applicable? Thanks for any suggestion.

Jeung