First to mention, I am not a gamer, not at all. My use of computers is somewhere between doing online social media things, regular office work and programming.
Besides watching videos, which requires audio, bringing us back to the audio issue, all other of my online needs are served fine by the RPi400.
On audio, I found a USB audio dongle which does play audio fine. However, the alsamixer is not able to control this particular device, therefore, the audio volume cannot be adjusted from the OS. My speaker has got a volume potentiometer, therefore, this is not a big deal in my daily life. However, it is not a solution for getting decent Bluetooth support.
The keyboard is good, although it appears to be a little bit smaller than others, which it is not. However, for unknown reasons, sometimes a keystroke is not recognized, in particular lighter keystrokes. From my experience, I create more typos than I used to with other keyboards. The solution that I found is stronger hammering on the keys, which however slow me down a little bit. Anyway, this is something I can live with and learn to adapt to.
The mouse is very lightweight. In the beginning that felt strange or even cheap. However, this strange feeling, in my view, came from the original mouse sensitivity settings in the GUI (openbox). In the "Preferences" menu, under "Keyboard and Mouse", I reduced the "Acceleration" from 5.0 to somewhere between 2.0 and 3.0. With less acceleration, the mouse feels a lot more comfortable to me. Also, the lack of weight does not play a role any longer, at least to my taste.
My RPi400 is configure to boot from USB. I am not repeating the method here, it can be found easily with any internet search engine. My choice was a SSD in a USB3 case. This gives a real speed boost over the SD-card as mass storage. Further, it allows for a lot more storage than on an SD-card.
Another advantage of an SSD is the safety of your data, due to the controller built in an SSD drive.
If I recommend any change or addition to a RPi400, this would be the one, get a USB3 SSD drive.
Networking works fine in principle.
Nothing to report about Ethernet, it just works.
WiFi, however, suffers a little bit from the design of the RPi400. Don't get me wrong, it does work, however, there is an issue worth to mention. The SoC is cooled by a big aluminium plate, which sits under essentially the entirety of the keyboard. In terms is passive cooling, this is excellent! However, this also provides a decent shield for the 2.4 GHz and 5 GHz WiFi signals. My RPi3B+ in a plastic case, receives my WiFi access point a lot better than the RPi400 in the exact same place on my desk. Network throughput is therefore lower with the RPi400. In case I am running a system upgrade, I therefore have an Ethernet cable handy, so that in case, I can full bandwidth if needed.
I am a longtime Linux user. Therefore, I am used to a certain set of tools. Up to know, I was able to find everything I needed in the repositories for Raspberry Pi OS (raspian buster).
For reasons of accessibility of RPi specific tools, such as Bookshelf and Mathematica, I opted for the 32-bit version of the OS.
One of the first tools I installed in addition to the preinstalled programs was synaptic. This package manager give an easy overview of what is available and what is already installed. It makes it very easy to add applications you will find helpful in your daily computing routine.
While my RPi400 suffices my present needs, in the future it is very likely that it will be extended by means of a powered USB3 hub, e.g. for card-readers, webcams, DVD-RW drives, etc.
