Yes ethernet allows sharing Waypoints (regardless of xducer configuration) ...
Waypoints are created at the GPS antenna location (not at the xducer location) ...
Waypoints are more accurate (to the underwater structure seen on the display) if the GPS antenna in closer to the xducer that is providing the Sonar data ...
When units are ethernet connected - every GPS antenna available in the connected network (internal and external) will be listed under the Network Source Menu ...
It's a good idea to rename each head unit in the Network Menu to make listings in the Network Source Menu more recognizable (default head unit names are serial numbers and makes it challenging to know which unit is which in the listings) ...
Rickie