Does macOS handle memory in a way where it just lets RAM fill up to some point before actively doing something about it? Because on my 16gig Macbook 8 gigs are gone just with browsing & spotify.
Yes. If you run vm_stat in the Terminal, you can see how few pages of RAM are actually left free at any given time. Modern operating systems aggressively cache files in RAM to improve performance.
The green/yellow/red graph in the Memory tab of Activity Manager is the best way of seeing if you need more RAM at a glance. In my experience, macOS won't do any swapping in the green. In the yellow, the system is still pretty usable but there's some swapping going on. When it turns red, your SSD will be getting thrashed pretty hard.
They're not really "gone", they've just been put to use because there's no point in leaving RAM empty. You can do much more than run a browser and Spotify with 8GB of RAM.
It's a good question -- do most people still use desktop office suites these days? I don't know the answer. I use the Google Docs suite for both work and for personal stuff, and I personally haven't seen the need to pay for Office in awhile.
My "typical Mac user" in this case, is my wife. Her 8GB MBP is holding up very well.