virtualbox.org

As subject says, does any Guest run faster/smoother with GA installed? specifically headless Guests accessed by remote (not vRDP).

Putting it that way, I'd say it won't matter if they are installed or not. In fact, the boot time and general memory usage will be a bit higher if they are installed, because of additional services that needs to start and keep running. That alone could very well be a performance hit, though usually unnoticeable. The only thing that would run faster, is video, but the generic VESA driver isn't used when you run it remotely (using either SSH or RDP). When using VNC like remote software, the video drivers could surely help in increasing the responsiveness and performance of the system.

Can you get headless without the GAs installed? Isn't the distinction between desktop and foreground windows something that the GA handles?

Ofcourse you can, GA is basicly only for desktop integration, but headless you need them for example for time sync, vboxtray can be removed in headless.

Sorry, I was thinking seamless, not headless. Yesterday was a long day...