Very nice read
I dont think nobody knows for sure but a few people have tried and tinkered with far red spectrum and found something they like.
Growmau5 used 3000k 80cri and added about about 15w 660nm and 5w 730nm per m² and some blues, dont remember what or how much, and was happy with that, no major stretch on his plants.
Stardustsailor, a very respected member who isnt really on the forum anymore recomended 2 parts 3000k 90 cri 1 part 3000k 80cri. He was using bridgelux cobs i believe.
All this to the best of my recollection.
Randomblame, uses a 1/3 3000k 90cri 2/3 3000 80cri i think, but ill let him answer for himself.
Dawg i think he used farreds in order to be able to flower with 5000k cause he wanted his sativas shorter, and got some results. In the end it depends what you want to do.
But this is only people and opinions. If you want scientific statements it gets harder. Broadening the spectrum in to the far red section seems to improve performance especially if you can control intensity and if you have, or are able to, balance of near red and far red.