My brother is 260 and rode my Canyon Spectral w/o problems, XL size.
I see you want an XC bike but I've been doing some testing of my Spectral vs. my buddy's marathon XC bike (Fezzari Signal Peak) and we're struggling to show a difference in speed between the two. We're testing on smooth laps as well as chunky ones with time, HR, and power, switching bikes too. Although the XC bike feels way faster the stopwatch, HR, and power data suggest the Spectral is running just as fast.
Note: our power data is difficult to interpret because I'm using power2max and he's using garmin pedals....but still, 8-10 minute laps within a handful of seconds with an average heart rate within 1-2 beats is what we're getting.