In my mind the main indicator we have for the severity of any strain/sub-strain/whatever is age of the infected. Younger and less vulnerable people getting infected just muddies the water, so to speak.
I'm also going to just plain disregard most of the data coming out in mainstream media related to covid. They have a false positive rate as high as 30% for the testing. There is a complete lack of transparency about basic data like specificity of the testing. There is an absurd level of corruption surrounding this virus. To speak plainly I do not trust mainstream statements on the virus. This is why the video I linked was produced prior to the covid outbreak.
I am aware that you prefer to believe what you are told to believe by the establishment. I'm fine with that. Just don't expect me to trust any official statements about the number of strains going around when they have a false positive rate for testing as high as 30%. Clearly there is an astonishing level of incompetence or corruption relating to genetic sequencing of this virus.
In any case, regardless of the above, strains aside... Viruses which require host mobility to propagate are selected against if they reduce host mobility and/or cause death. Human assisted natural selection of the virus is taking place.