Glass helmets in OB?
* General loot, yes, but only up to a certain point. At lvl 20 you should still only find items of lvl 5-10.
* Powerful unique items, yes. Otherwise you'll end up with a power character in the next playthrough, way too early.
* Powerless unique items, no. If items have only an aesthetic value (like some should, rather than everything being enchanted to kingdom come), they don't need to be scaled.
* General bandits, yes, but in suitable intervals. If you cleared a route, it should stay cleared for a good while.
* Wildlife, no. Startup wildlife should be static in that you simply can't expect to survive everywhere.
* Main quest, yes and no. Some scaled that you know you can handle. Some unscaled that forces you to wait.
* Side quests, yes and no, depending on the reward. But no more "go fish" where you come back after a few levels and the fish slaughter you more easily
* Important NPCs (like the single one having that last piece of armor), no in general. This one may have undergone training since last time you met him. Maybe killing his trainer would leave him at last level?