Dave does your Helix 9 have SI or DI? If not I don’t believe you can see the SI or DI screens on the 9. They most likely are not available views. Go Menu Menu and then Views to see if there are any DI or SI screens.
No any unit with a N as part of the name ie 2GN 3GN etc. can be networked together. Networking will allow you to share weigh-points, temp and depth readings but if one of the units does not support SI or DI it would not have the software to display the screen.