The overhead will mostly be redundant usage of memory, but this shouldn’t be too bad as we’re constantly making sure this is where it needs to be. We don’t plan on doing anything like sharing assets across instances since this probably isn’t worth the complexity.
For ports, you specify the initial port in the ini, and then inside IpNetDriver.cpp we’ll pick the first available port from there.
For security, if you are using a single instance, if one player was able to find an exploit, it would affect all players on that machine rather than be confined to that single instance.