None of this seems related to LLMs. Propaganda produced by humans is effective because of the massive scale of distribution, being able to produce more variations of the same talking points doesn't change the threat risk.
Being able to produce more variations of the same talking points sounds really useful for increasing the scale of distribution - you can much more easily maintain more legitimate looking sock puppet accounts that can appear to more organically agree with your talking points.
I don't think it moves the needle much at all. At the end of the day the scaling bottleneck is access to gullible or ideologically motivated eyeballs. The internet is already over-saturated with more propaganda than any individual can consume, adding more shit to the pile isn't going to suddenly convince a reasonable person that vaccines have microchips inside.