As of this writing, Windows 10 on ARM is an ARM64 platform, which only supports 32-bit x86 apps via a built-in emulator. It is not possible to run traditional 64-bit apps in this OS. Earlier, we mentioned that this will eventually be changed. It looks the change goes live.
It looks like Microsoft is working on 64-bit (x64) app emulation for Windows 10 on ARM PCs. The feature might be introduced in 2021, removing limitations on software use on ARM PCs.
During WinHEC 2016 (Windows Hardware Engineering Conference), Microsoft made the announcement that they are working together with Qualcomm to bring Windows 10 to Snapdragon ARM mobile processors. It looks like Microsoft has already started uploading ARM64 builds of Windows 10 to Windows Update.