Lofi delay: feed the V/OCT and FM inputs a negative voltage offset (or positive inverted with the attenuverters) to drop the frequency below audio rates, and turn Damping up to max or near-max. Sympathetic strings mode works really well for it, but the other modes can too.
Feedback: literally just a feedback patch where you mix some audio signal with a Rings output of Rings, and patch that mixer into Rings’ input. Maybe insert something else in between, like a wavefolder. I like matrix mixers for feedback patching. You’ll probably want a VCA after the “final” output and/or before the Rings input.
Feedback can cause some clipping/saturation within Rings, which then activates additional filter bands in the resonator – so you can feed it a sine and get rich violin- or horn-like tones out of it.