Can this be used with a gopro?
How much weight will this carry? i'm looking to mount an atomos ninja inferno.
3.3 lbs or 1.5 kg. is it's stated limit.
Is it strong enough to handle high speeds around 125mph on a motorcycle?
That would DEPEND on what type of camera you are going to use and HOW much WIND resistance the camera is going to create!!! If you tighten it down enough it will hold.
Otherwise as for the structure and material of the Ulanzi Super Clamp - in my opinion I would believe this clamp will hold a light GoPro with ease in that environment.