Hello,
I have a same question about the very same topic.
I'm new to modular and started to get interested into this since few weeks, but have years of experience with guitars, pedals, synth, noise machines, etc.

My possible approach to a modular system would be to have something that I can both use stand alone (like in a drone/noise/ambient manner) or together with my guitar and synths and made so that I can implement/interface it also with instruments levels so that I can rout it thru my guitar pedalboard for example.

I did some experiments with VCV Rack, and found very powerful a combination of Plaits and a second VCO/oscillator combined with a quad LFO to generate sounds and drones.
After talking with a friend and try out few his modules, I also got very interested about Schlappi and Noise Engineering modules. For example I like a lot the Desmodus series, since the same module can be loaded with all firmwares available. Boundary looks like I swiss army knife that I can use as VCO, envelope, etc...
But I also find Doepfer modules to be super cool, simple and utile to what you need them for.

I would like to keep it as small and compact as possible, like 64HP. After few mindstorms, I came up with this first idea, pictured below.

My only concern at the moment is the Strymon AA.1: are there any other alternatives out there for such "guitar interfaces", so that, as said, I can insert my guitar (or another synth) into this system and then go out back into my pedalboard?
What modules to you use? Otherwise any other advices?

ModularGrid Rack