A question for quality

Hi,

I did export from ScreenFlow ( ProRes with Alpha 422 ) in 1280 x 720, then import to FCP X -> Send to Compressor and at 12.000 BitRate I'm not happy with the quality.

* I wrote again here ( it was a different question ), I'm new to all these so please accept my mistakes.

If I export to 2560 x 1440 the quality is pretty good.

Is there any option when I make the video full screen to keep the same dimensions of my main video and to add black bars around it without make bigger the main video at all ?

Or that depends of the player ?

I'm asking this because I see the little distortion happens only when I make the video full screen. The video tries to fit on the screen and the result is bad quality.

I make the project 2560 and the Clip 1280. I chose Spatial Conform -> None but the quality is even worst.

Thank you very much.