The learning curve is a bit steep but his guide is awesome https://trash-guides.info/Radarr/Tips/How-to-setup-language-custom-formats/
In the other hand, the public trackers are dominated by English and, at least I, I couldn’t find a lot of Spanish dual movies better than the 720p
In any case, if you can gain access for a Spanish private tracker with radarr support, let me know
Take a look onto he following image: https://i0.wp.com/www.techjunkie.com/wp-content/uploads/2016/09/tv-size-distance-chart.png?ssl=1
There is always a subjective component in this kind of discussions but this image will help you to see if yiur setup will make sense based in the real perception of the human eye.