When I first started making Kraut, I added several different adjuncts, like coriander seed and Fennel seed and even put some shredded beets in one batch. Then one time, I submitted some in a County Fair competition, I was dinged for adding anything except cabbage and salt.
So I learned to be a purist when it comes to Saurkraut...and I do like it that way. Not to say I would dislike onions and jalapenos in there...but now I just use cabbage and salt...and only the whitest layers of cabbage, yes the Fair judging will ding you if it isn't white as snow.
As to Fresh from the garden.
I started out buying cabbage from the grocery store, and it turned out fine. But when you use fresh picked-same day, you get lots more juice when the baseball bat is introduced to it. More juice means better fermentation and a bit more acidic product in the end.