To convert DVD movies to play on Plex, Android or Iphone devices use the following:
I now use MakeMKV to extract files from DVDs or Blu-Ray, then I use the current version of Handbrake to compress to .mp4 files.
Download and install DVDDecrypter (see link below).
Use the IFO mode and select none for the file split
Pick your source and destination, check the stream processing to make sure the right language is selected. Start the rip with the green button.
Download and install Handbrake
Select the source, destination, preset format, and save. I like to Iphone & IPod preset for both my Galaxy tab and Iphone viewing. The image is streatched to full screen automatically and the movies are about 500 MB each.