The ability to pick something up easily, make some progress, pause it, and resume quickly at the next available window appears the best way to go.
Then you want the steam deck. This thing is powerful enough to run elden ring at a pretty stable 30 FPS, sometimes even up to 60, while being portable enough to fit in a backpack. I take it with me on business trips and it’s perfect for flying, bussing, wherever, with the caveat that you want it plugged in more often than not - the battery life is a little on the low side for those high-impact games.