It is indeed a great price for such a cool computer, although the partnumber RPI400-KIT-IT indicates that this is a kit with an italian keyboard layout.
You can buy any microsd card and flash it with the tool you can download from the raspberry site, which lets you choose several operating systems depending on what you want to do.
Unfortunately, we can't make a specific bundle with what you mention. ):
The solution would be to choose the parts you need individually.
https://www.galaxus.ch/search?q=rapsberry%20pi%20400
No, the RAM cannot be changed on the Raspberry Pi 400. The Raspberry Pi 400 is only available with 4GB RAM, and no 8GB versions are built. If 8GB is required, the 8GB version of a Raspberry Pi 4 must be ordered.
This information in the shop about the 1500 MHz is not correct, every Pi 400 is clocked at 1.8 GHz. The Pi 400 has a very large heat spreader made of metal that helps to cool the CPU. No worries, your Italian Pi 400 will also run at 1800 MHz with all cores and it will not overheat.
The simplest solution is to use an external USB SSD. As a completely ready-made solution https://www.digitec.ch/de/s1/producttype/externe-ssd-2591
The choice for a size of 250/256GB is not very large, because it is too small for most people. The entry-level size is more like 500/512GB. There is a larger selection available there.
Or do you want to put them together yourself? In a cheap SATA 2.5" version e.g. the following combination:
Icy Box IB-AC703-U3 (2.5")
Crucial BX500 (240 GB, 2.5")
With an SSD, you should simply remember that the smallest sizes also have the smallest lifespan (TBW).
The question is recurrent, but I have not yet seen an answer from digitec/galaxus.....
Is it possible to have the QWERTZ version .... or at least QWERTY (so USA) of the raspberry pi 400 to have a keyboard as close as possible to CHF-FR or CHF-DE but to have the guide in the local language. So for example in French. (and not the French version with the AZERTY keyboard which is not used in Switzerland...)
My ideal would be a rapsberry pi 400 with QWERTZ keyboard and a guide in French.
If no CHF-fr keyboard...
Then a rapsberry pi 400 with QWERTY keyboard and a guide in French.
Is it possible to mix the packages like this? Or is it independent of digitec/galaxus?