Just purely out of interest - if an executable intended for Windows Mobile is run on a standard Windows operating system, what happens? I ask because when downloading an installer package intended for Windows Mobile onto my Windows 10 machine, Explorer shows the description and developer info in a tooltip.
I think you'd get a "This app cannot run on your PC" as the majority of Windows Mobile devices use an ARM processor, and the majority of PCs use x86/x86-64 arch
The actual binary files (.EXE, .DLL, etc.) will either not work at all (if they are compiled to native code) or - if they're purely .NET intermediate language - will start to load but possibly fail to get very far because the runtime libraries between the phone and desktop OS are somewhat different. UWP apps that are not compiled to native code can work on both the PC and the phone, assuming they aren't flagged as only supporting one or the other, or require hardware the PC lacks.
The format of both the executable binaries (PE format) and the application packages (.APPX or .APPXBUNDLE, which is just a ZIP archive with some required contents) are the same between the phone and the PC. This means that tools (such as Windows Explorer) that read the metadata of such files will have no problems. However, that doesn't mean the code within those files is compatible across all platforms; in most cases it will not be.
The most significant hurdle would be - as @theLMGN pointed out - that phones run ARM CPUs, while (most) PCs run x86/AMD64 CPUs. AMD64 is backward-compatible with x86, but neither one can run ARM machine code (without an emulator).
My bet is that executable files use the same format, but rely on different libraries, so you'll see some error message about missing libraries or functions. If Windows developers detect these files specifically (like 16-bit executables), you may get more meaningful error messages.
Either way, you won't be able to run the files.