Yeah, 40km buffer in the mountains when you haven't done the route yet isn't the most confidence-inspiring situation. You should go to evtripplanner.com yourself and do the route for your X, that may give you different (better? worse?) numbers. The first trip is always the "most interesting", then you'll get a hang of the car's travel capabilities.Wow - I love this forum!
But if rkm is 276, that only leave me with a buffer of about 40km (100% charge is 320km). Yes, I will be going in summer, but maybe I better charge at the Sicamous visitor centre as you suggest. (I don't have dual chargers though).
In terms of speed, you're telling me that going slightly above 100km/hr doesn't make much difference from 90km/hr? Then I would rather go at the higher speed.
We've taken multiple US trips on interstates and I don't see a significant difference between 65 and 73, but I don't record all the numbers to the 7th decimal place either. And there's the physics aspect of wind resistance that is truth no matter what my feelings are. So don't trust me!! But I agree I like the faster speed. At least you should be no-holds-barred for all the other legs.
My 70km/hr charging from the 90A at Sicamous was unfortunately based on dual 40A internal chargers but I guess you only have the 48A single in the X, I forgot about that. If you were planning on a straight shot to Calgary, yeah that will make things somewhat slower. We generally stop in Revelstoke overnight, but then we're calculating leaving from Tsawassen after the first ferry docks -- you have much better time options.
If you haven't charged to 100% yet, that last 10% (from 90%) takes like a half hour. On our 85 it's 30-40 minutes to 90, then nearly all that again to 100. Just sayin', just in case.