I have mini PC similar to this one called a MintBox Mini from Linux Mint and Compulab and though completely different machine the concept is similar, low power silent running etc.
In the BIOS are settings for Power draw and amount of RAM to allocate for Graphics. The default settings were useless when I first go the machine. Particularly the power setting which was 4.5 Watts which I change to 8.5 and totally different machine.
There is also a setting for the amount of ‘shared’ RAM to allocate to Graphics that was, like yours, 256MB so I cranked that up also.
4.5 watts and 256MB might be fine for other uses but not as a desktop PC.
This would seem a good place to start. Mine had only 4 GB RAM and I gave it 1 GB for graphics. 512 MB might be enough but it works fine with Linux on it.
These machines, at least mine, are set to low defaults from the factory as that is there selling point and being passively cooled these defaults assist with ‘cooling’.
I have 2 of these machines (Mint Boxes) both lower spec than yours and they are fine for Youtube or videos mp4 etc but useless until I turned the power up from 4.5 watts. It acts like a governor or restrictor.
Looking at he MSI website I see ‘supports’ on several specs such as 4k video, doesn’t mean ‘works’ out of the box as I discovered upon delivery of my mini PC’s.
If this machine is new to you and you’re setting it up with Linux for the first time then these settings, if present, might be as good as anywhere to begin.
The power settings might be listed under ‘thermal’ or APU thermal or some other non-obvious name as was my case.