@KristjanESPERANTO since you got me curious, I looked into Wayland a bit.
So to answer your question again:
While Wayland is generally considered more efficient in general use scenarios, in a scenario where you want no window management, no window decoration and certainly no visual effects, that efficiency advantage would not only be negated, but turned into a disadvantage.
Also unlike X11, Wayland apparently cannot be started as a bare-metal service but always requires a compositor like Weston or Sway in the background which would actually not only result in a heavier premium in resource usage but would also require a more complex and error-prone setup.
Last but not least, wayland is far less use-case agnostic compared to X11. Like many modern software suites, it makes a lot of assumptions about how it is going to be used. Since many, if not most of these assumptions wouldn’t hold true in a scenario like the one we’re discussing here, using Wayland would carry a lot of the downsides of running MagicMirror on a full DE, in short, you’d be fighting against your framework instead of working with it.
In conclusion I can say from what I learned about Wayland so far, I definitely made the right choice with X11.
N.B. that are only the conclusions of a very brief look into Wayland on my part, so there may very well be ways to make it behave the way I want it to, but if they exist, they seem to be a lot less trivial and well-documented.