I don't what you mean by 480p (I know what it means just not what you mean). I used standard composite cables. And I've finnished GTASA on it and I've played through about half of JSRF. On normal crt TVs. Didn't have any issues and I only played them from hdd through xbmc.
480p is via the HD adapter and component cables. It's the best resolution available from the Xbox. If you run it on 480i, aka with composite or s-video, you won't have issues.
He's talking about games that don't work or have issues when using the component cables, ie, 480p or 720p on 1.6a/b Xbox revisions. If you are using a Scart or composite cable, then you won't have the issues specified in post 1. The issues to be more precise is, some games have issues displaying in 480p on 1.6 Xbox, they don't seem to initialise the video mode properly & you end up with a black screen or a scrambled image. There are workarounds, like forcing 480p via NKPatcher (softmod) & disabling it in the dashboard setting, or using a loader to load the game after the video mode has been set, ie, CDX.
I don't know where you heard that 480p is the best resolution for the original Xbox but that's incorrect. The original Xbox can do HD at 720p and 1080i. Very few games supported it but it is supported. You just have to go into the dashboard and change the video settings to "this display supports 720p" and "this display supports 1080i". Also, YPbPr Component video won't be the best video option for the Xbox in about December or January when OzOnE's Universal HDMI mod board comes out.