connection to other brands modules?

Yes and no. First up, it's important to note that interconnecting an AE system to anything else first involves establishing a groundplane that includes both the AE _and_ the other device(s). This is a typical issue with any single-point patching systems...Serge, etc. If you have a number of devices that you want to "hub" off of the AE, you might find it easier to set up a grounding bus for ALL of those devices as a default, just to make sure that that critical step is done before proceeding.

Next, the AE system does have some voltage differences from other modulars. You're constrained to a 0-5V range, and there's no negative voltages. As a result, it's necessary to use devices that can enforce this voltage scaling difference; the AE system's 4I/O can do this for either DC or AC signals in four channels, plus there are inexpensive devices like Soundmachines' Nanobridge that can provide "protected" I/O that references the AE's primary voltages to accomplish this. I actually use both: the Nanobridge I have is for CV/gate/trigger connection/regulation, and I use 4I/Os for audio interconnection, giving me a total (if needed) of 22 interconnection points in my system.

As for cables, if you only use a 4I/O, you're just fine with using 3.5mm cables between it and whatever else. But in the Nanobridge's case, you have to connect its GND and +5V references to the AE _first_, and THEN you can patch all of the 3.5mm cables you want between it and the other device(s). But if you don't make those initial connections, you won't have your overvoltage protection working before you patch other signals into the AE.