Looking for a new computer–explain to me how RAM works...

As far as I know, Adobe recommends at least 16 GB for each of those three programs: InDesign, Illustrator, and Photoshop. If you're running them all at one time, and running other stuff as well, I would expect that you would need more than 16 GB of RAM.

If you keep Activity Monitor open to the Memory tab while you run a heavy workload, the Memory Pressure graph and other information at the bottom of the screen can provide some information.

The Memory Pressure graph is color-coded. Green means that macOS thinks you had enough RAM for what you were doing. Yellow means that macOS thinks the amount of RAM was marginal. Red means that macOS believes that there was not enough RAM and that this was likely to have been causing performance issues.

Here, my Mac had 7.91 GB of completely idle RAM, and another 9.36 GB of RAM that it could give to programs at a moment's notice, but that it was putting to work holding "Cached Files." The idea here is that if a program needed any of the cached data, the Mac could save a slow trip to the SSD (yes, SSDs are slow, compared to RAM), or to a mechanical hard drive, to get it. If a program wanted the RAM, instead, it would be safe to dump the cached data because the original data would still be present on the drive.

Swap Used is 0 bytes, indicating that the Mac was never so pressed for RAM that it had to use space on the startup drive to simulate more.

Memory Used falls into three categories:

• Wired Memory is for things that must remain in real memory; that cannot be swapped out to compressed RAM or to the startup disk. That includes, for instance, structures that the operating system uses to keep track of virtual memory, as well as things like buffers for the monitor. The Mac wouldn't be able to deliver a steady, high-speed stream of data to the monitor if it had to pause and go to the drive to get some of that data.
• Compressed Memory is like Swap – except that it is to RAM. The theory is that modern CPUs are so fast that it is better to have them burn some cycles compressing blocks of memory ("swap out") and uncompressing blocks of memory ("swap in") than to have them waiting on a slow SSD or mechanical hard drive. Using compressed RAM for the first level of swapping also has the advantage of reducing wear and tear on the SSD.
• App Memory accounts for the rest of the real RAM currently in use by macOS and applications.

What you are seeing is something that causes many uninitiated to assume they have not got enough RAM and therefore need to buy more.

Mac computers are designed to use most of their RAM all the time even though they may be simply idling.

This means that if you had 128GB RAM your Mac would be using around 100GB or if you had 8GB RAM it would be around 6GB.

FWIW I have never had more than 8GB RAM on any Mac and I do 1080p and 4K video editing with Final Cut Pro and DaVinci Resolve with no problems at all.

So the base model with 16GB should be plenty.

The Blue Chunks wrote:

Feel a bit silly asking, but I have a 2017 iMac with 40 gigs of ram I use every day for design work, generally keeping InDesign, Illustrator, and Photoshop open, as well as music, a browser window with a bunch of tabs open, and maybe a text editor or Word.

Occasionally I use it for music (Ableton/Bitwig, nothing complex) and video editing (Adobe apps).

Activity monitor shows 30 GB "Memory Used."

I opened up about the same set of stuff on my M1 (16gb ram), and it showed only about 14 GB "Memory Used."......

Thanks

Look at how much swap is used on the M1. This is stuff that is temporarily moved to disk to make room for foreground processes. I am willing to bet that could be quite large if you are really using all those apps at once.

You likely may not see that much of a performance hit vs. the iMac because of the speed of the M1 and its SSD. However, it does add wear and tear to the SSD over time which does have a limited life time.

Not rocket science: many open tabs & programs plus heavy photo-video editing = get as much RAM as you can afford.