What specific effect does the armor property PowerFac have? I've never been able to intuit it just from the name, and have not done intensive behavior testing with armor to figure it out. What "power" is it affecting? Everything else is self-explanatory (aside from figuring out whether positive or negative changes are detriments or benefits).
It's badly-named "Acceleration" factor. It determines how fast you accelerate when walking/running up to your armor's max speed. It's barely noticeable unless it's under 0.25 but is very interesting. Even at 0.0 you'll still accelerate, so you can get some funny movements with a 0.05 PowerFac and a 5.0 SpeedFac. Though at 5.0 speed you run the risk of being able to sprint through walls.
Thanks. I considered it might be a poorly named acceleration factor, but as you noted PC acceleration is generally not a noticeable issue. If the value was limited enough to make it noticeable then it would be an unnatural irritation to the player. Oddly, even though penalty properties were finally added to the "transportation" boosts, this was not one of them even though added portage mass would certainly affect acceleration.
PowerFac might not work as intended anymore due to the Character Controller changes, we have to look at that