Portability/modularity/plus I have an Intel Arc GPU. The drivers just played nicer on Windows when it comes to transcoding (which you said wasn’t an issue.) But most of my services are on separate barebones VMs because they’re just easier to work with.
I went with a “traditional” desktop because I already had a big ass Be Quiet! Dark Base 900 Pro. Also I don’t trust hardware raid, and a regular desktop is infinitely more flexible.
For instance: I threw two GPUs in there! Little one for transcoding, big one for gaming. So I can play a game while my girlfriend watches a movie in the other room. Plus I can keep shoving drives in there until I run of room. A dedicated NAS is much more limited
Hah well, I just tested the built in graphics and it worked. If you wanna give me more details on what you have I can try to help