Deciding how much memory your new Apple silicon Mac needs is one of the more irreversible choices. As its memory is mounted in the chip carrier and there’s no way expand it later, what you get in the first place is all that Mac will ever have until it goes for recycling. Add to the fact that Apple silicon Macs use their memory differently from Intel Macs, your guess as to how much you need might be no better than mine.
Knowing that Apple silicon Macs don’t have separate graphics memory but use main memory instead can mislead you into paying for more than you need. For example, my Intel iMac Pro has 32 GB of memory and 8 GB on its graphics card. Add those together, and you could easily assume that an equally capable Apple silicon Mac would need a minimum of 40 GB. Thankfully, that’s not the way it works. To understand why, let me take you back to how your Mac generates what you see on its display.
WindowServer
Every app is responsible for drawing the contents of each of its own windows. They are then passed to WindowServer, which composites together all the different windows over the Desktop, and passes the rendered composite image to the graphics card to display. In most better Intel Macs, the first stages up to and including WindowServer take place using that Mac’s main memory, but when WindowServer hands the composited image over to the graphics card, those contents have to be transferred from main memory to that on the graphics card.
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