mqtt or createServer causing Uncaught CWMODE failed: Timeout

Glad it's working now! It'd be interesting to know which commands were causing the issue as it's possible I might be able to do something in the driver to work around it...

Just from a design perspective, it does make sense to do certain things if and only if the wifi actually made a successful connection

That should actually be the case in the handler supplied to wifi.connect( - when you get called and err is not set, you're properly connected with an IP address.

L6 and L15 will execute within microseconds of each other,

This is not the case at all, since 'connected' is called when everything is connected.