2 Ions on a network

No, Any console that is able to output (Primary or backup). Will take the lowest output count. So If I have a ION (1024) as primary and a ETCNomad (512) backup as. Both Consoles will be downgraded to 512 as the nomad is the lower count. While they are connected together.

Clients have no effect on the output count as a client does not take over control of the rig in the event of a primary going offline.

You could of course use them both as masters controlling different universes and then sync the cue steps with osc commands from one to the other. Probably not very practical unless perhaps you have something like a matrix display that is going to eat loads of addresses where you could use the second desk to drive that with the first one really running the show and just triggering the second one to do something with media on the matrix as and when.