From my understanding it varies from airline to airline.
I’m looking at the Air Canada page that has details for example which can be found here.
But I’m not sure certain what it means.
Can I have a portable power bank that’s 160W? If I bring that could I also bring on a laptop and a Steam Deck?
It seems like you can bring 15 devices theoretically.
https://www.catsa-acsta.gc.ca/en/what-can-bring/guidelines-batteries
I’ve never been asked to open my bag by an attendant in the plane. Generally the battery checks are done in the carryon bag scan by CATSA. So if you have a 160Wh (Watt hour) or smaller battery bank, and if a battery bank is considered a device rather than a spare battery, then you should be okay to have them with you.