I haven't tested T5NO lights, nor have I seen any data from anyone else for them. I do know that T5NO lights are more efficient than T5HO - more light per watt - and T5NO lights are a bit more than half the wattage of T5HO lights. So, a T5NO light should produce more than half the light that a T5HO light does, but only if it has the same quality of single bulb reflector. Unfortunately, I don't think any T5NO light does have the same quality reflector. I think the best guess I can make is that a 2 bulb T5NO light will produce about the same PAR as a typical one bulb T5HO light. I suspect it produces less PAR than that.
And, remember, AH Supply PC light fixtures have uniquely great reflectors. Coralife fixtures, for example, don't have nearly as good reflectors. And, many cheap PC light fixtures effectively have no reflector at all, because they allow no room for one. They might produce only half the PAR as an AH Supply light.