So far I've got a Ricochet doing octave up duties and a Bass Whammy for harmonies, going into the Joyo American Sound, then a TC Mimiq.
The Ricochet sounds great; also you can turn it on in latching mode, then switch it to momentary mode so that pressing the footswitch will do divebombs! In terms of realistic octave up, both Digitech units do a great job, but the Bass Whammy in classic mode is better for riffs low down on the E string. I'm on the lookout for a cheap Whammy V, MicroPOG/NanoPOG/POG2 and Pitchfork to contrast and compare.
The Joyo nails the dirt sound, and the Mimiq adds
stereo doubling which helps separate the 'guitar' from the bass. Sounds perfect through headphones / monitors, so no need for guitar amps!
Looking at adding a Radial Twin City ABY to split and select the signal chains, and experimenting with some fuzz in front of the Joyo. Playing like this is tons of fun, more so than playing a real guitar!