PowerShell is a very powerful tool and can do pretty much anything with any Microsoft product, including UWP Apps.

To find where an appx is installed you can use the command Get-AppxPackage -Name PackageName.

The package names are usually very hard to guess, for example the current name of the Netflix app is "4DF9E0F8.Netflix". Some app names have 0 relation to the name shown in the start menu.

To make it a bit easier, you can use the Where-Object instead of the -Name parameter.

Get-AppxPackage | Where-Object {$_.Name -like "*flix*"}

This will look for any appx packages which name matches *flix*.

The result on my computer is this:

Name              : 4DF9E0F8.Netflix
Publisher         : CN=52120C15-ACFA-47FC-A7E3-4974DBA79445
Architecture      : X64
ResourceId        :
Version           : 6.93.478.0
PackageFullName   : 4DF9E0F8.Netflix_6.93.478.0_x64__mcm4njqhnhss8
InstallLocation   : C:\Program Files\WindowsApps\4DF9E0F8.Netflix_6.93.478.0_x64__mcm4njqhnhss8
IsFramework       : False
PackageFamilyName : 4DF9E0F8.Netflix_mcm4njqhnhss8
PublisherId       : mcm4njqhnhss8
IsResourcePackage : False
IsBundle          : False
IsDevelopmentMode : False
NonRemovable      : False
IsPartiallyStaged : False
SignatureKind     : Store
Status            : Ok

In the C:\Program Files\WindowsApps\4DF9E0F8.Netflix_6.93.478.0_x64__mcm4njqhnhss8 folder I can see that it's a WinJS app written in HTML, CSS and JavaScript.

There's no Netflix.exe in that folder?

There's not. I don't think you've ever seen a Netflix.exe (unless it's a virus). Here's a screenshot from my Task Manager while having Netflix up and running.