What is power armor anyway?

That’s the point. I said 5-10 encumbrance per set. That means light PA would have 5 points, which is less than what you’d get from wearing a shirt and light jacket. High encumbrance will come from covering it in holsters and carrier packs.

The way it looks means nothing. It protects against radiation and gas in vanilla, but I intend to change that.
Even then, radiation isn’t gas. You can have a set of concrete walls that block all radiation, but you could still walk around them.

Maybe they aren’t ceramic or rubber?

An ANBC suit with servos would be light power armor, not basic. Basic is more like an MBR vest with servos. Think the mk1 Iron Man suit.