I have some 1080p 24fps videos I want to burn to a dvd-r disc. Will DVD architect automatically scale it down or should I render the videos in 480p before importing them to dvd architect?
DVD Architect is able to re-process it and scale it down -- but you'll always get the best results when you give the program video that is as close to its final output format and resolution as possible.
I recommend using Vegas Pro/Vegas Movie Studio to output a DVD-ready version of your video file.