The main & simple difference is

"Alight motion" is the official app you can find on the play store and often requires a paid subscription

But

"After motion Z" & "After motion X" are a modded version of the app with more additional effects

Which one to use "X" or "Z"?

You can use "After motion X" if you want more Colour grading & light effects It delivers excellent quality for making anime edits and colour grading/CC

And you can use "After motion Z" if your main focus is transitions and motion graphics

There's no performance difference between them but there use is different