If you haven't already, check out the sticky "fermenting peppers 101" in this section.
Regarding cannedkraut, I don't think canned kraut has the live bacteria that is needed to kickstart the fermenting process. The heat process of canning the kraut will kill the bacteria. A cold-packed refrigerated kraut would likely have the bacteria still in it. Kimchee would also have some.
Size, just make sure there's enough headspace for the chiles to float without touching the airloc or lid.
good luck and have fun~