Location being a Vector, you can set an index value to get only X,Y or Z. But since OSC offers more possibilities than the MIDI protocol, it's now possible to send and receive the whole array of values (for vectors or colors).
When you set a route to receive a full array, you have to make sure that the number of values sent matches what Blender expects (and it's required now to use the "n" parameter accordingly). For colors, for instance, it can be either 3 or 4 values depending if there is an extra Alpha channel added to the R,G,B triplet.
"From" and "n", allow to extract in a list of messages a subset by specifying the rank of the first item and the number of items. "0" is the item just after the OSC address (like /blender) and generally doesn't need to change for simple message. "n" however has to reflect the size of the targeted Blender array.
Pick button: This allows to automatically fill the Address based on the last received OSC message.
Multi routing: Please refer to the MIDI multi route settings as they are mostly the same. In the context of OSC, the purpose is to address messages like the ones presented by Face Cap. Notably the 52 Blendshape parameters (Shape Key values) formated like this:
/W + 1 Int + 1 Float (blendshape index, value)
When enabling the multi route for OSC, the add-on will search for an index at position "0" of the list and affect it to "VAR", consequently you have to set the "From" parameter to "1" to pass the index and focus on the payload just after. With the Face Cap Blendshape parameters "n" will stay on "1" since there is just a single float value to pick.
Note: OSC multi routes can now send. The add-on will insert the index automatically for you.
Note2: the index in multi routes should counts from 0 (for the first item).
Note3: if you use the new actualization mode "expression", be careful that IN may represent an array of values, and that your expression should output in this case an array of the same size. Fortunately Numpy, a scientific module for Python make easy to manipulate arrays (or even simple value most of the time) and is exposed thru the "np" prefix.
"0.0.0.0" allows to listen to all the network devices of your computer, you might want to restrict that later but it's handy for tests. The connections are updated as soon as you change a parameter if enabled.
The input connection can sometimes appears in red, this reveals a problem with another software blocking the port. The server will try to reconnect automatically and revert to the normal as soon the problem is solved on the other side.
The 2 switches allow to disable temporary sending or receiving.
The "Debug" option will copy in the console a report as soon something is received by the add-on. For that you need of course to start Blender from a shell window. Be carefull, it adds some extra computation.
(Note: theses 2 features are still in beta)