Welcome back to boating! good times ahead
so the new HDS7 carbons are a few lightyears ahead of where you would of left off with your older HDS series units. better.....everything. Even the previous Gen3 series are rather good. having two of the same makes for a great case of networking. of which the HDS can do. the Go series from simrad cannot.
first question A: no you wont have issues if set up correctly. "selecting the right transducer and sonar source"
option two questions
1. yes it will work with the simrad Go xse with the use of a Xsonic plug adaptor "lowrance of old uses a blue 7 pin connector. newer lowrance carbon/simrad units use a Xsonic 9 pin plug pretty easy to do. (gen3 HDS still use older blue plugs)
2. no issues running two when set up correctly.
its a bigger world out there now. plenty of brands and models to suit everybody.
Moose