I use MakeMKV to rip all of them. I don't want my movies compressed because it kills the quality. My DVDs are usually betwee 4-7 GB and Blurays are anywhere between 18-40 GB. Plex can stream your MKVs perfectly as long as you use the right device to stream your MKVs. If you are using Firetv or Xbox or Chromecast...you will likely have problems streaming MKVs because they cannot directplay. So you will have to stream them at lower qualities so they can transcode...which sucks. Use a New Roku 2 and it will dominate MKVs or anything else you throw at it through plex.

I have well over 10 TBs of movies in MKV form and My Roku is great for it.