Movie purchased via itunes won't synch through TV app

Moved to the TV app last week as movies no longer appeared in iTunes in Windows 10. Using devices app I synched my ipad and had to transfer purchases. I then synched my iphone in the same way.

In my iTunes library for movies I found two copies of films that I had on each device. I deleted the film with the '1' in the name. I now find that the iPad cannot find the file that I left in each folder, but my phone can.

Does this mean each device I synch has its own library so I have to retain two copies of each movie on my computer?

How does this fit with my backed up iTunes movie library of over 800 films - if I put a folder back into iTunes movies folder on my PC will they synch to my device? I don't want to have to re-download every movie when I want to watch as it was faster for me to just copy a file from my back up and use iTunes Edit menu to paste to my device. There seems no way to just do the same with the TV or Devices apps.

Any assistance gratefully accepted.

(Tagging iTunes for windows as there's no option to tag any of the four Windows apps).