www.makemkv.com

I tried using search but the board doesn't allow searching for 3 letter words.

I'm new to ripping 3D blurays and am not totally sure I'm doing it correctly. For example, The Meg shows as having two instances of the AVC stereo stream, both identical size (around 33GB).
Does this mean one is for the left eye and the other is for the right eye?
When creating the MKV am I supposed to rip both of them to get proper 3D playback?

No it just means there's two virtual copies of the movie on the disk - e.g. with different audio tracks, or maybe a different title sequence for another language.

Pick either and make sure you expand the title and select "MVC Video 3D" to include the 3D video data. Your next challenge (because it is a challenge) is to find a player that can render it to your TV without dropping the 3D element and only sending the left eye data.

I can recommend the Vero range for playback .. but there's not much else will do this.