Hello. I am new to dvdr scene but not kvcd

recently got me a NEC 2510A dual layer 8x dvd writer. I have 2 dvd movies i want to backup onto 1 dvd+r media i believe with KDVD template this is possible. I have calculated the total size of a 4.7gb dvd disc in bytes to be able to calculate target size mpg for tmpg encoding. Before i go anywhere else I have 2 questions:
1) on the KDVD full template is it best to leave min bitrate at 300 and max at 5000 cause with kvcd I had my min bitrate at 64?
2) on the KDVD template i noticed that the GOP is set to 15 where as with KVCD it was 24? can someone explain this?
I have Tmpg DVD Author and was wondering how easy this is to use as i would like the menu and chapters from the 2 movies i put on 1 dvd+r media.
TIA.