Is there a way to avoid recompressing an MPEG-2 file that has modifications, like choosing interlacing with top field first and selecting high VBRs? I think the recompression will result in loss of video quality, which I'd like to avoid, if I can.
Just make sure that 1) your MPEG2 files are DVD-compliant and 2) your Project settings (or the individual clip settings in the Optimize DVD window) match those of your videos. As long as these two things are true, DVDA couldn't care less what field order you use or what your bitrate is set at.