All of your advice is viable.

There is a lot of different stuff being talked about as one. FWIW this is a fencerow nozzle. It's a goofy 360 degree thing so I can't attach a picture.

https://www.spraysmarter.com/hypro-boom-x-tender-fence-row-spray-nozzle-03931ca4c77a6f980d21609d4846dd31.html

But it operates like this.



Generally, it takes a separate valve and operates with the outside boom.  

If you are looking for something like this, don't ask for a fencerow nozzle.  I've never seen a nozzle like this, but it appears it is what you need.  You might be able to achieve the same thing with an evenflow nozzle on the outside pass and then switching it to whatever other nozzle you are using.