As everyone has emphasized, setup is a female dog.
The one that is 1-1/16" in cutting length is probably your best choice for 3/4" stock. For anything less than 3/4" stock use the smaller bit with the 3/4" cutting height.
Any lock miter bit rarely uses the extremities of the cutting surface.
As far as set up goes . . .
Page 131 or so of the book, "In The Craftsman Style" has the best explanation of how to set up the bit.
In the Craftsman Style (In The Style): Fine Woodworking, Tim Schreiner: 0094115583985: Amazon.com: Books
Don't hold me to the exact page number but it is close. (I'm doing this from memory and I haven't seen the bock in about 5 years.)
The bad news is, "You'll never get the cut exactly perfect." You can get it close and then sand the joint.
As for reality and making legs, simple miters are just as good. You don't really need the extra gluing surface. Use blue tape to align the legs and then clamp. It works exceptionally well and the results are strong legs.
If you are making drawer boxes using Baltic Birch, a simple rabbet or locking rabbet works very well. With the simple rabbet, a trapped bottom can be made without the dado showing. With the locking rabbet and finesse, the same result is possible.