WHDLOpener is an AmiNET package that installs E-UAE along with many extras in order to be able to run games within Ambient, the MorphOS screen manager. The default settings are alright but they could be adjusted for a little better result and some QoL.
First, the E-UAE settings can be changed in order to make some important changes, namely getting the games that run in full screen to properly go fullscreen and also to stretch the E-UAE emulation window to match the entire monitor size as it is configured for MorphOS. The settings involve editing the E-UAE configuration file for the fullscreen mode.
Next, WHDLOpener is configured to start games directly in fullscreen but most of the time when browsing games it seems much more helpful to run the game windowed on the Ambient desktop by default rather than start in full screen mode. In order to change this, the mime settings must be amended for all files configured by WHDLOpener. This can be done by going to the Ambient desktop, right clicking and then following the menus Settings→Ambient…→Mime, expanding application and scrolling down to find x-amigaos-whdload. By clicking Edit, the Run in E-UAE (window) menu option ca be made the default on double click with the full screen Run in E-UAE still available using the right click menu when a WHDLoad slave is selected.