No, the Y cable is electrical connections. One leg of the Y cable has the electrical circuit for 2D sonar and the other leg of the Y cable has the electrical circuits for SI and Temp.
There is no possible menu changes to select the 2D sonar crystal in the SI transducer since there is no electrical connection for it.
2D sonar would come from the shoot-thru all the time.
You cannot share CHIRP to a non CHIRP unit.
When networked, you can control the 2D sonar separately, but if you adjust the SI Range with either unit, it changes both units.
The unit that does not have a transducer connected should have Sonar OFF.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, 360, RC-1