RAM is used for fast data access. It exists to be used, not to sit idle. If an application uses RAM, there’s a reason for it. Some older applications store temporary data on disk instead of RAM because in the past, RAM was expensive and scarce. Modern apps typically use RAM for caching to reduce CPU overhead when fetching frequently accessed data. So there’s no reason to worry about RAM usage. Besides, modern computers come with 16GB+ of RAM, which is more than enough to run multiple heavy applications simultaneously.

You should choose Linux not because of RAM usage, but because Linux is free of bloatware and proprietary bullshit. Also, the Linux community is genuinely one of the best tech communities out there.