Someone who's more experienced can address this as well, but I've been exploring Ringen a lot more recently, so I'll offer my thoughts.
It seems that Ringkunst is essentially grapple-only, kind of like modern college wrestling. But Kampfringen is a mixture of the grappling of Ringkunst with a bunch of other elements, in particular "dirty tricks" (eye gouges, ear rips, throat strikes (halsfassen) finger breaks and tears, etc.) and a handful of fundamental strikes, including punches, palm strikes, elbows, knees, and kicks. If you do a good study of kampfringen, you get those basic techniques, but they're used as an adjunct to the grappling, kind of the way that atemi-waza works in Japanese jujitsu.
I don't know how many sources you'd need, but I'd personally start learning about Kampfringen add-ons that are present in the manuals as a starting point. Sorry if I can't be more specific--I'm only just starting out on it myself.
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