The fans on mine kick in only if it's doing resource-intensive stuff, like running a VM. If it's just normal usage -- web browsing w/ loads of Safari tabs open, a YT video playing in a PiP window, playing music with Spotify, just to name a few -- it gets a bit warm, but stays pretty quiet, otherwise. And while I know the high-pitched key thing is something others have dealt with, I myself have not had the issue. I haven't pushed the machine hard enough, and/or for long enough, to know.
Regardless, yours definitely sounds like it's a lemon. Good thing you opted for a replacement -- I know something like that would drive me crazy.
Do keep us posted!