I got 17 apps open in both OS X & W10 in Parallels. I'm just below 1GB free memory. Chrome on both OS's w/about a dozen combined open tabs, Visual Studio, SQL Mgmt Studio, 2 other code editors, email, messaging apps, and a bunch of other stuff, and Activity Monitor, of course. And can likely open more stuff if needed.
I don't usually have this much open at once, but good to see my 8GB machine is handling it OK.