[noggin]

A last question:
You see on the pic (second link) HDMI is:  Current HDMI mode YUV 420 10bit Rec.2020
This is my HDMI settings. This is for default because I enabled the best quality of HDMI on my TV. Now I have to choose the color space on Shield TV. I made some tests and it seems the best options are:
RGB 8bit Rec.709 and YUV 420 10bit Rec.2020.
In your opinion which one is better to choose?
Thanks

  
As I said previously - if your content is Rec 709 - chose a Rec 709 output. If you chose Rec.2020 then your Shield TV will convert from Rec 709 to Rec 2020 - and your TV will handle this as SDR Rec 2020 (which some TVs handle differently to SDR Rec 709 in gamma/EOTF terms)

Rec 709 to Rec 2020 conversion isn't always a good idea on every TV. If you don't need Rec 2020 output for other apps, don't use it, and use Rec 709.

I'll try and convert your H264 to H265 for you so you can try that.