You can run the emulator with a different screen size: https://codefrau.github.io/Smalltalk78/?width=640&height=480

There’s also an Alto mode https://codefrau.github.io/Smalltalk78/?alto which is closer to what folks used to work with back then

As far as I know the Tektronix Smalltalk computers (4404 and later) were the only ones to try a higher resolution scrolling virtual screen.

For Alan Kay's talk they removed some limits of the original hardware, like screen size, processor speed, memory limits and storage (floppies in the original). They found that without these limits the experience was actually better than more modern Smalltalks in some ways. Sort of like using a 1980s 8 bit microcomputer with a modern SD card.