Do people in Tahoe heat-tape their whole roof or just the edge where ice dams would otherwise form? I've only ever seen the latter, and even doing that will be noticeable on your power bill.

also idk, tons of people up here have regular sheds for various purposes and they seem to survive just fine

Cascade mountains. I've seen over 5 feet of snow in under 48 hours, then freezing rain. Its heavy! Lots of these "it'll be fine" type structures collapsed.

Building code for snow load is a factor of location and elevation here. We are around 130 lb/sq ft.

Roof pitch can help with shedding, but then you've got other problems (roof avalanches can and do kill, not to mention snow up against materials that don't want to be wet all winter).