The appx contains the entire shipping game, including that content folder. Appx is the package distribution format for UWP apps. It’s essentially a zip plus some metadata. You can actually give it a zip extension, unpack it using the Windows shell, and go look to see what’s inside.
The Store will ultimately want an unsigned appx (included in that appxupload archive). The Store signature will be applied to your package once it has been through certification and is ready for release. You can’t, however, install a packed-but-unsigned app on any Windows 10 device. So when you want to test a packaged app before you submit to the store, that’s when you go through the process of creating and installing your own certificate for signing. In Developer Mode you can install a loose, unsigned app. This is what you are doing when you use F5 in Visual Studio, or when you use the Project Launcher in UE (without a custom profile that includes packaging). In this case your app is never put into an appx; instead, it is laid out on disk with the file structure that would be packed, and then a special, Developer Mode only registration step is run that allows it to run from this location (Powershell equivalent: Add-AppxPackage -register [path to appxmanifest.xml]). This is the workflow I recommend for day-to-day iteration since it avoids the packaging and signing steps, both of which take some time.
You shouldn’t worry about your final appx size too much. As someone pointed out above, we’ve shipped fairly enormous games like Gears and Forza. That said, there’s a new feature in the Windows 10 Creators Update to improve the user experience when downloading large packages: Streaming Install. It’s not part of our UE integration though, so would require additional engine customization work to add.
To get started with Xbox Live, you’ll need to be part of either the Creators Program or ID@Xbox. Creators Program is currently in preview and requires that you apply, but will become fully self-service. It’s a great way to start. Once you’re in you can get your Title ID and Service Configuration ID (SCID) from Dev Center, which you should then add to your UE project settings for UWP. The integration uses these to automatically generate the xboxservices.config file described towards the end of this page. Note, however, that we’re not currently adding this line:
"XboxLiveCreatorsTitle":"true"
You’ll need to manually add that, or else change the generation logic inside UnrealBuildTool (UWPDeploy.cs). I intend to make a change at some point so this can be toggled through project settings - or someone is welcome to PR me one!
Once your app is associated with Live, you can sign a user in via
IOnlineExternalUI::ShowLoginUI
Note that this might skip UI completely if the system is able to sign the user in without interaction.
Phew! Hope that all helps!