These sticks definitely do not have the cooling capacity to run at full rated heat output 24/7. As you note, they're passively cooled. They don't produce any less heat than a Chromebook on the same SoC, they just throttle and downclock faster.
I meant "passively cooled" as their advantage. You can always place some Noctua on top of them if needed, you just don't have to. I have one of RK3188-based sticks which is enclosed in a passive case. I also run the latest Bay Trail NUC in passive mode 24/7 and its temperature is higher on heavy load than of that Android stick. Performance wise BT is about 2x as fast, though it depends on a task. 9W vs 14W at full load including OpenGL, 1W vs 4W at idle.
