The HP Pro Mini 400 G9 has USB-C ports, but these do not support Thunderbolt. Therefore, you cannot connect it directly via Thunderbolt to a monitor that has an integrated docking station. However, you can use a USB-C dock to get additional ports as long as the monitor supports USB-C. Alternatively, you can use the HDMI port to connect the computer to a monitor.
The HP Pro Mini 400 G9 is a business computer - not really made for gaming. You can play Minecraft on the best computer, but it will be a bit jerky and not much fun. If you want to play Minecraft, I recommend a desktop computer/laptop that is made for gaming. They have an extra graphics card that can handle the game better.
These requirements are covered very well by the Mini PC, but there are fans in it and you will hear them sooner or later. They can also break down. A complete and fanless Mini PC would be possible with the Zotac CI645 box, because there is guaranteed no fan in it and it is completely passively cooled with a large cooler and heat pads for RAM and SSD. The CI645 Zotac box also easily covers all requirements. It's available from about 475 and you'd have to add another 100 francs for 32 GB RAM, about 80 francs for a 512 GB SSD and another 100 francs for Windows 11.
Zotac ZBOX CI645 Nano (Intel Core i5-1135G7)
Laut Kingston unterstützt dieser PC keinen ECC-RAM-Speicher.
https://www.kingston.com/en/memory/search/model/104806/hp-compaq-pro-mini-400-g9-desktop-pc
Er sollte Non ECC RAM wie diesen unterstützen:
Kingston KCP432SD8/16 (1 x 16GB, 3200 MHz, DDR4-RAM, SO-DIMM)
If you compare both products, you will see that the cheaper PC is obviously an import product from Germany.
This becomes obvious when you look at the manufacturer's numbers.