I've found over the years of dealing with 'hybrid' control systems that if you have something that works as a manual control, then implement it as a manual control. Plus, if you're not sending envelope CVs over the ES-8 setup, that frees up a channel or two to send something else, like a cross-rhythmed trigger or a counterpoint CV. So, I would suggest leaving the ES-8 in place specifically for sending clock, CV, and gate/triggers only, but also using the ES-8's return inputs to have Silent Way (or whatever is doing the CV/gate sends) track activity on the modular. That way, you can have the software reacting to actions generated by the synth, setting up a control feedback loop. For doing more complex things, generative work...this is very useful. As for the rest, envelopes, LFOs, and so on, these really work better as 'hands-on' control devices so you can live-tweak these parameters instead of being 100% locked into what the computer says to do. With that, you get variation, and variation is key to making music 'human'.