A128 & Chirp

[Natch]

In an earlier thread, I requested and received immediate assistance, concerning water temp readings, with just an in hull transducer and the CP 200 module. As I learn more, using my two Raymarine MFDs (A127 & A128) following the transition from Lowrance to Raymarine, I am appreciative of having someplace to go for answers. Accessing menus to make adjustments and setting changes can be a bit challenging, when you have become so accustomed to procedures of another brand for the last dozen years.

I want to get everything I can out of these units, so I figured this was the best place to pick the brains of Raymarine experts. With that, I have a couple of more questions.
I'm not sure which transducer is epoxied in the bilge, which is connected to the A128. However, like the Gen 3 Lowrance, Touch units, the Raymarine A128, has Chirp circuitry built into the unit and should work with a standard 200kHz transducer.
Am I wrong to assume that, because I can't find a chirp selection menu?

Also, this boat was equipped with twin A128s, mounted side by side at the console and a single A127 at the bow. I had no need for the dual set up at the console, so the seller flush mounted a 128 in the dash. So, currently, there are two transducers being read by the A128. The presumed 200kHz in the bilge and the Side Vision transducer feeding info to the CP 200 module behind the steering wheel. I'm assuming that I need to add a CP100 transducer to the back bone to able to use down vision. Is this correct?

The A127 at the bow has a CP 100 transducer mounted to the trolling motor and it provides clear 2D sonar/down vision and water temp, so the fishing end of the boat is fine. Both units read my Navionics chip, which is installed in the 128 as I have both units linked

Thanks in advance