M wrote:
* Since I'll use Canadian ATC service during the overflight, will I
get a bill from NavCanada when I get home?

I often fly IFR over, and occasionally to, Ontario, and I've never
received a bill. Maybe it's just me.

* Is it easier to do this IFR or VFR? I assume doing this IFR would
make the Canadian overflight easier, but I'm very open to suggestions.

I've been under the impression that Toronto Center would rather not
provide VFR radar service. If only for that, I think IFR is easier.