Mac storage basics · Memory, swap and speed
Will a Mac with more memory (RAM) use less disk space?
Short answer: Only slightly — with more memory macOS needs less swap on disk, but swap is temporary and rarely why a disk is full. Memory and storage are separate.
Only slightly. When memory runs short, macOS writes some of it to swap files on the disk. With more memory it needs less swap, so a busy Mac with little memory can use a few extra gigabytes of disk that a better-equipped one wouldn't.
But swap is temporary and shrinks again when the pressure eases — it's rarely the reason a disk is full. Memory and storage are separate things; buying more of one doesn't add the other. See swap files and storage vs memory.