You are intending to burn a standard DVD, these are typical settings that will be used to create the final video.
The Field Order can be Lower Field First
The Video Data rate of 8000kbps is suitable for a 60 minute video.
If your video is longer then this figure is reduced, at 4000kbps it will allow for 120 minutes of video.
24 bits, 720 x 480, 29.97 fps
Upper Field First
Video data rate: Variable (Max. 8000 kbps)
Audio data rate: 256 kbps
Dolby Digital Audio, 48 KHz, 2/0(L,R)
You are mixing HD and DV-Avi, as you know one uses Lower and the other Upper.
You can only have one field order in a video file so one of them has to change.
Unfortunately changing the field order will affect quality, usually showing Jagged lines.
You have to decide which order to use.........
As a test convert a sample Dv-Avi to the properties above Mpeg2 (Upper Field), then convert a sample HD to Mpeg2 using Lower Field, play each, which one looks the best?
If they look simular then choose the shortest
Convert the DV-Avi video to use Frame Based, then convert the new Frame Based to Mpeg2 Upper Field, does this video look any better.
Microsoft AVI files
24 bits, 720 x 480, 16:9, 29.97 fps
DV Video Encoder -- type 1
PCM, 44.100 kHz, 16 Bit, Stereo
Video Data rate
You seem to indicate three 60 minute Dv-Avi, maybe i just read this wrong.
The longer the video the lower the data rate, a lower data rate gives lower quality.
How long is your final project going to be.?
Once you have decided on a Field Order and a Data rate create a template using make Movie Templates Manager.