I think another difference between hypervigilance and paranoia is that you are allllways conscious of it with paranoia - you're consciously aware of being worried that X is going to happen. I think hypervigilance can be a lot more subtle and something that isn't being done consciously - you just become innately more aware of surroundings and will pick up on tiny changes without always even knowing what it is.

Like... paranoia is walking down the street and being super worried that someone is going to jump out at you, so you're constantly looking over your shoulder and scared and looking around corners before going. Hyperviligance would be like walking down the street and feeling ok... and then you notice a movement out of the corner of your eye and freak right out - to discover it was a leaf blowing across the street.