DVDs require MPEG-2s. There are presets in the Output Module that allow you to select an ideal (though not necessarily optimal) setting.
DVD authoring apps require strict adherence to DVD standards. So, you do need to stick with 720×480. You should scale to fit the height of 480. Your width will be larger than 720. YOu can center the composition as it is or re-position it on the x-axis.
HTH
– Roland
TypeGEMs – the Definitive Type Gizmo for AE
https://broadcastgems.com/typegems/
Intensive mocha & AE Training in Singapore and Other Dangerous Locations
Adobe After Effects CC ACE/ACI
Imagineer Systems (mocha) Certified Instructor
https://www.broadcastgems.com/mographintensity_shapestext/