I seem to recall that the screen settings depended on the attached monitor.
The Mac Plus and similar, of course had 512 by 384 as only possible setting. I would have to dig out the specs of my Mac monochrome and colour monitors to see whether 512x384 was an option, but I guess it was - if only for compatibility reasons. I know my NEC Multisync could do it, though I hardly used it.
BTW, Basilisk II may be set to 512x384:image uploader
MiniVMac runs with a 512x384 screen by default too.
I guess much depends how screen sizes were patched into the MacOS for emulation.
Real Macs had sense pins at their video output to determine which screen resolutions a given monitor could do.