Quality bonuses and potency bonuses

Quick question about the Playtest rules. Higher quality weapons automatically grant a bonus based on quality. For example an expert quality long sword gives a plus one bonus. If you add a plus one potency rune to that does it gives a plus two bonus?

Also, how would such a weapon be described? Is it a plus two long sword or is it a plus one expert longs sword?^

The bonuses given by quality and by potency are both item bonuses, so they do not stack.

Before you put any runes on, your expert sword is described as "expert longsword" (the +1 on attack rolls is implicit).

After you put a +1 potency rune on, your sword is technically described as "+1 longsword," the quality being implicit since it's the minimum possible to have a +1, though "+1 expert longsword" isn't actually wrong.

If you put a +1 potency rune on a master longsword it would be a "+1 master longsword." (It would then have a +2 item bonus on attack rolls for being master quality and do 2d8 damage for the +1 rune.)

Potency and quality don't stack you use the better of the two. Since potency runes requiere a minimum quality the way they seem to describe it in the book is just a +X sword and assume the quality is the minimum necessary for the potency rune which also means its item bonus is equal or less than the potency bonus. Still it's probably good to include both so you know what would be requiered to add property runes or to upgrade it further. I like quality +X weapon ordering myself: Expert +1 Longsword.

Re: naming conventions - Bardarok is correct in that quality is omitted if it is the minimum required quality, however official material will normally follow a "potency, quality, properties, type" format.

An item with runes etched on it is typically referred to by the value of its potency rune, followed by its quality (if that quality is higher than the minimum required for its potency), its properties, and finally its item type; for example, a +1 longsword, +4 legendary fire-resistant chain mail, or an expert flaming kukri.

where in the playtest rules does it clarify that the item quality does not stack with the potency rune? My players will want to know lol

If you gain multiple bonuses of the same type, only the highest bonus applies—you don’t add them together.

Item Bonus: Weapons and skill-boosting items of expert, master, and legendary quality add the listed item bonus to attack rolls with the weapon or skill checks using the item

A weapon potency rune grants two offensive benefits. The weapon’s wielder gains an item bonus to attack rolls with the weapon equal to the potency value. For instance, an expert dagger with a +2 weapon potency rune would grant a +2 item bonus to attack rolls with the dagger.