Apple TV and downloaded iTunes movies

As I live in an area with a bad internet connection I would like to download iTunes movies and play them on my TV.

The problem is that when I use airplay to play movies the picture quality is worse than when I stream directly. I have used airplay from both an iPad and MacBook. I am air playing to an Apple TV 4k gen 2.

Can anybody help m,e getting a better result from Airplay - or advice on other ways to play downloaded movies?

Thank You!