Don't use the external preview from the Vegas timeline to create a VHS tape. You can certainly record whatever is being sent to your external monitor, but there will likely be glitches and you may end up with lower resolution.
To create a VHS tape, do one of two things:
1. Use the Print to Tape facility, but don't put a tape in your camcorder. Disable camera control, and when the print to tape is ready to start, push the record button on your VHS VCR and then click on the Vegas button to start the output of video.
2. Render the video to a DV AVI file, and then use the Print to Tape feature of the "Capture" utility to send this to your camera. Again, disable the camera control, and manually press the record button on your VHS VCR at the appropriate moment.