Thanks for your replies and extra info. I agree with
@W4RR10R that indeed the Ryzen 3600 seems the best option in every way, as it is much better in applications and stands it ground in gaming. In the reviews it is often compared with high level Intel processors and it does a great job. Exactly why it makes the 3600 so interesting IMO.
But what the reviews don't generally compare (well), is power use and temperatures. I understand very well that most people are interested in benchmarks and framerates, but I want a small PC that doesn't sound like a jet airplane or turns the room in an oven (imagine turning the oven to 90 C and leaving it open on a warm summer day). For me that is more important than 10 frames more or less in a gaming situation.
I have been monitoring reviews on the internet, but only found one additionally interesting. It are actually 2 different reviews from the same site (Techspot), one in which they review the 3600 and an older one in which they review the 9400f (versus 2600x). Cross-referencing the results (yes, it is not completely accurate, as different parts were used) provides e.g. the following info;
Division 2 average (1080p, Ultra quality settings)
3600: 157 fps
2600x: 142 fps (138 in the other test)
9400f: 143 fps
Shadow of the Tomb Raider average (1080p, Ultra quality settings)
3600: 95 fps
2600x: 87 fps (88 in the other test)
9400f: 88 fps
Not much news here, but the reviews point out that the 2600x and the 9400f run around 70 C degrees (load, using box coolers) and that the 3600 runs 80 C degrees (load, using box coolers). For a SFF build that would be a bit too much for my liking (I am planning to squeeze it in my trusty Sugo SG05). Especially knowing that the Intel box coolers are bad, and as such the 9400f can easily be pushed lower with a better cooler.
This seems a bit in line with what
@prayogahs previously reported.
Links to the reviews:
https://www.techspot.com/review/1871-amd-ryzen-3600/ and
https://www.techspot.com/review/1829-intel-core-i5-9400f-vs-amd-ryzen-5-2600x/