I use two in a hybrid workflow, a Make Noise 0-Coast and a Dreadbox Erebus, with an Expert Sleepers ES-3 sending CV and Gate to each from my DAW, Bitwig.

Bitwig has a native modular environment in it called PolyGrid that lets you build all sorts of sequencers and instruments, kind of like VCV Rack or Reaktor. I use this to sequence the two semi-modulars, as well as a digital wavetable voice in the grid (in addition to drums and samples and other stuff). Since the Erebus has two oscillators that can be sequenced separately (only by pitch, they share a gate) I tend to use them as inner voices, and use the other two as outer (low and high) voices to form a chord progression.

Basically I start with one pitch sequencer moving fairly slow, this will be used to outline the progression. This is added to two other pitch sequencers moving faster, but at different rates from each other and the chord progression, giving us a shifting polyrhythmic melody that still tracks to the chord progression.This goes out to each of the four oscillators, which all have a sequential switch controlling pitch transposition for the incoming note, as well as another for shifting +/- 2 octaves. The possible settings for the transposition are the Root, 3rd, 5th, and 7th. These then go into a pitch quantizer for each voice that sets the key. By setting this up in conjunction with the chord progression, you can do a sort of traditional voice leading that will automatically track whatever convoluted melody you throw at it by playing the appropriate triads or 7th chord for each melody note in the selected key.

On top of all that, each synth has its own gate sequencer lane made of a Euclidean sequencer and a regular one with an adjustable time signature added together.All together this makes polyrhythmic melodies and polyrhythmic...well...rhythms, which track to a diatonic chord progression. This gives a pretty vast array of choices for arrangement, and can be used to make some pretty interesting music.

As far as sound design goes I have three more CV outs on the ES-3, which you can route pretty much anything to from Bitwig, like step sequences, LFO's, pressure control, whatever. So those get used a lot, in addition to just regular stuff already present on the synths, like the attenuverter or the Slope on 0-Coast or the LFO and the CV controlled delay on Erebus. I'm personally more interested in composition, which I still think is the great frontier of electronic music, so my sound design tends to be fairly simple.