High-Quality Weapons and Armor

This rule basically says that a "+1 devastating" sword works like a +1 striking sword, except it isn't magical. It gives the same bonuses and costs the same, but doesn't penetrate magic resistance, and cannot have potency runes.

If you etch a potency rune to any non-magical weapon the weapon becomes magical as usual. Since high-quality weapons and armor gives the same bonuses as magical weapons and armor, these do not stack.

See: https://2e.aonprd.com/Rules.aspx?ID=1368 (no changes from the rule as written)