Your ethernet hub will work, you’ll just need the adapter cable for the Helix which is about 12″ long and the appropriate length cable to your hub.
You can share waypoints, that would be the extent of the sharing due to a Helix/Non Helix configuration setup.
I’ll be swapping my 800 series units with 2 Helix 9 Chirp MEGA SI+ GPS G3N.
Will be keeping one of the units on the dash for mapping only and networked to the Helix units and Ipilot Link
From the Humminbird web Networking Chart:
Ethernet Cable = AS EC10E, AS EC 15E, AS EC 20E or AS EC 30E, selecting the length needed. If more than 30 feet is required, purchase AS ECX 30E plus additional length
1 Waypoints, routes and tracks along with i-Pilot Link, 360 Imaging and CHIRP RADAR are shared. NMEA 2000 can be used at the same time with one drop direct to ONIX/ION and one drop to the NMEA2000 Gateway.
2 CHIRP Sonar will only be shared with other HELIX networking models with software version 1.350 or higher.
3 MEGA Imaging sonar will only be shared with other HELIX G2N and newer models or with other SOLIX models.
Chart Link for compatibility and cables needed:
https://www.humminbird.com/support/faqs/NetworkingChart
Hope this helps