I think the mIRC Options dialog settings should be set according to the network you're connected to, instead of setting options for all the connections. This would make it more configurable for multi-server connections.
For example, let's say I'm connected to three different servers. On server 1, I decide I want mIRC to cancel away on keypress. Well I would simply enable this feature by ticking the checkbox in the Options dialog. This would only effect server 1. The rest of servers would remain the same, unless of course, you change the settings for each server. Know what I'm saying?