Worth double-checking, but I think that's one area Mituharu's is better than standard Emacs. I definitely recall some font rendering issues with some past version.
As for your other points, they aren't resolved. FWIW, I work around them:
> The server mode compatibility
I just have one long-running Emacs session. I have some colleagues who have experimented with using a launchd LaunchAgent to start emacs server in the background when they login. I haven't kept up with their results and I don't know if there are any side-effects.
> "Windows" (or Frames?) have generally not worked seamlessly for me
Since I have a long-running session, this isn't much of a problem for me. That said, when I do start up Emacs on first login, it indeed takes upwards of 5 seconds to startup, including a window re-themeing and resizing. It's not great, but like I said, it's only once at startup for me. Furthermore, because I came from a tiling window manager on Linux (AwesomeWM), I required similar behavior on macOS. I use SizeUp [1] with shortcuts configured to move my windows to side/corners of the screen. It's far from being as good as a true tiling window manager, but I've had to be satisfied with what I can get.
[1] https://www.irradiatedsoftware.com/sizeup/ (there are alternatives like Moom)