Sorry for the delay in coming back to the thread.
As far as the start layout in the multi-app kiosk config there's a default option to have the app tiles on a full-page start menu so I went with that and didn't do a customized layout.
I also followed up on this with a Microsoft resource and according to them for that built-in Edge option to work Edge has to be assigned to the machine in Intune (something I'm unable to do currently because the client apps workload in our environment is still Configuration Manager only).
One small bug I found is that if the show taskbar option is selected File Explorer will sometimes be displayed on the taskbar, seems to show up randomly after reboots.