That's really interesting, I personally don't read those tone differences based on the casing. Neither approach carries different warmth or formality to me at all.
I wonder if this is a regional or generational thing?
It's definitely primarily generational. In my experience, capitalization-as-tone is used by many Generation Z people. On the other hand, it is not widely used by older generations, or the younger Generation Alpha.
In my experience, that isn't the case. Among people who "have gotten used to" it, using capitalization to indicate the formality and/or tone of your message allows the reader to understand the writer's intention better. I have not observed any correlation between political leanings and this.
I'm not sure what you dispute or your point is here. If people slightly or strongly start aping Trump's writing style in various forms I'd say there's a good chance those people are right wing or simply "not the same people writing in all lowercase" you know?
You highlight stylistic choices. I'd say we can observe the differences in different styles and see how uses them. Is Trump writing in all lowercase? No. Is this poster writing like Trump? No. Do a lot of left-wing people use the all-lowercase style? I see it all the time, yes.
I wonder if this is a regional or generational thing?