How does equipment scale regarding sidekicking and WvW?

In PVE, in the process of leveling up, you find better armor and weapons, and those have better / higher stats.

Assuming you're level 50 with appropiate-level armor, what stats are given to you when you're scaled down? Does the stats given by the equipment remain? How does it scale?

Now, opposite case in WvW: since you use your PVE equipment but you're scaled up, how does the equipment scales? Having a full 80-set with appropiate stats is much superior to a lvl 50 character with appropiate-level equipment? How does that work?