

Regarding the future uniforms, the same uniforms appear in most portrayals of “future starfleet” during the TNG era, such as DS9 The Visitor. I don’t believe they are meant to indicate a connection between alternate futures beyond being the next step for Starfleet uniform designs (although the uniforms shown for a similar time period in Picard turn out to be different anyway).
Regarding your question more broadly, yes. And also no. Both, really.
I’m not sure Q recognizes or cares about the distinction between spinning up an entirely bespoke simulated reality for Picard to do his thing in, versus altering the past such that branching timelines are created and shuttling Picard’s consciousness between them before ultimately closing them off. Or whatever other myriad mechanisms an omnipotent being would have for triggering the events portrayed. Nor is there any real way for us the viewer or Picard the participant to distinguish between those things. What is real, what clearly matters both to Picard and to Q, is that Picard did pass a test, and that Picard remembers those events in a way which will influence his future actions and relationships.
There was organized violence deployed by groups of humans against other groups of humans long, long before anything we would recognize as warfare. Particularly brutal violence too, because the objective was not to conquer other people (something which only makes sense once agriculture is the dominant mode of sustinence), but to either drive off or exterminate a rival group so you can use their territory for yourself.
And we don’t even need to talk about people here: we have records of chimpanzees fighting small scale wars of harassment and extermination against neighboring groups.
Pre-modern, pre-civilization, pre-aggriculture, pre-you-name-it human life was far more violent than what we deal with today.