In the bay area every home I've lived in had 20A circuits for everything.

The NEC 80% rule is only relevant in data centers where someone enforces it. The time-current curve for any 20A breaker shows that it will take infinite time to trip when you draw 20A. This is correct behavior because 12awg wire can handle 20A indefinitely

Do they actually install the 20A outlets with the sideways part? I don't know if I've ever seen one in person.

I guess the outlet doesn't matter a whole lot, especially if you take multiple cables to the wall.

But I still don't want to be doing unenforced electrical violations.

Some outlets have the 20A sideways part, but from a safety/code perspective that's irrelevant.

Consider what happens when you plug two 10A devices into a power strip. In the US there are no true 15A rated outlets. All outlets must handle 20A because the electrical code allows any outlet to be on a 20A breaker.

> Consider what happens when you plug two 10A devices into a power strip.

I don't know about any argument that depends on such an action being safe. There's plenty of power strips I wouldn't trust with 20 amps.

That's just how the US electrical code works. I assure you that every "15A" outlet on the wall can handle 20A. That's why products like this don't have a fuse: https://www.homedepot.com/p/Woods-2-ft-12-3-SJTW-Multi-Outle...