| | Re: t5 HO or NO
It's both, actually - put a normal bulb in an HO fixture, it'll still have a lower output than an HO bulb. And, like Michael noted above, an HO bulb in an NO fixture doesn't do much.
Most HO ballasts can take a NO bulb, but doing that makes it just a more expensive NO fixture. And unless you're inclined to do your own wiring with Home Depot light strips, most of the options on the (aquarium and/or hydroponic) market are HO anyway, so IMO you might as well just get the HO bulbs and fixtures.