For my Raspberry Pi 4 computer, I had a cheapo plastic case with one fan that worked ok, keeping the RPi4 cool enough (no heatsink, merely the fan blowing out hot air from the case).
However, I had some reservations to it as the fan did make some sound (I keep the RPi4 running pretty much 24/7), the fan uses some power which in turn just makes the RPi4 maybe a bit hotter in itself, and the increased airflow of course brought dust inside the case.
Anyway, two weeks ago the fan died, after mere few months of use. Maybe it was the dust, I don't know, but even after I cleaned the fan, it wouldn't rotate anymore. So I used the RPi4 without the fan and the top of the case, and the CPU temperature would reach throttling levels (85 C or so I think) quite easily, in moderate loads.
So I decided to order the passive-cooling Flirc case for which I've seen some good reviews: https://flirc.tv/more/raspberry-pi-4-case
I had to order it from Germany as I didn't see any Finnish online stores selling it, but whatever, it came from Germany in a couple of days with DHL to my door, delivery cost something like 9€.
Damn I am happy with the Flirc case. It was easy to set up, and it really does cool the RPi4 CPU quite well, without using a fan. The highest I've seen the CPU temp go so far has been around 60 C, under a 70% CPU load or so. And no sound from any fans, or dust going inside the case. Great!
When you touch the case, you really do understand why it works so well: the aluminum case can feel quite hot to your fingers. I like the simple design as it seems to work so well: the whole case acts as a heat sink. That's great, as long as you don't have to hold the device in your hand.
That had made me wonder and wish, shouldn't also PC laptops, and why not even desktop PCs, use these kind of designs to make thermal cooling even better? Of course with laptops the problem is that you don't want to make the keyboard feel too hot so it would still need to be insulated from the rest of the case somehow.
That's kinda why I am wishing my next gaming laptop would have a whole-metal case (e.g. aluminum or magnesium alloy), to make its cooling more powerful. Not the plastic cases which insulate all the heat inside, and hope that the heatpipes and fans can push it all out with air. My understanding has been that the Intel-designed laptops partly use this kind of design, to improve the cooling of the components. https://www.youtube.com/watch?v=YlkFUB_XLVs
I use a Raspberry Pi myself, using a case that came with a fan, though I am not using the fan. One thing that helps deal with throttling is when I remove the top of the case, at which point the blinking thermometer icon will disappear.