It looks like you are expecting too much from a CS18. It's a CONTROLLER for the RM mixers, borowing 6 audio channels from the RM. Two audio lines use channels 31+32 = AVB 31+32, two use AVB 33+34 and the two other (AVB 35 +36) simply give access to the monitoring section of the RM rack mixer. That's all there is and will ever be. You need an AVB switch to use "audio over AVB", which does not mean what you think. A direct AVB (!) connection between a RM mixer and a computer (Mac) is possible. A CS18 will never be able to send its signals to a computer via AVB. But with FireWire between RM and computer, yes, certainly...
For using DAW mode you need a router (not an AVB switch), because UCNET looks for Strudio One and adds it to the AVB network via WLAN. This wakes up the buttons on the CS18AI. But there is no audio involved. Audio stays on the RM rack mixer and the data transfer between mixer and computer happens via FireWire. In this setup, the CS18 is just a controller for Studio One, but it gives faders to Studio One... ;-)
The CS18 and the RM are legacy products. Do no expect any further development any more. The only thing PreSonus will do is keeping CS and RM usable with upcoming OS versions for a limited time (a few years).