Were the giant warriors created by Man? There were references to them being created so I assumed they were but their origins were unclear.
I always saw them as an allegory for nuclear weapons.
I kinda thought they were soldiers of the apocalypse. Or something....
Yes, they were bioengineered by humans. They can act autonomously but were also capable of being piloted/controlled as well. You actually see what was left of one towards the start of the movie when Nausicaa climbs up into the robotic skeleton of one to see what was happening with Yupa(although, at that moment she didn't know it was him being chased by the Ohmu).
Living is easy with eyes closed
Misunderstanding all you see