For those who have not read it elsewhere, and if your Mac is recent enough, according to Apple's Announcement, macOS Monterey 12.0.1 official release will be made available next Monday, 25-October-2021. My personal guess would be at 10:00 USA - Pacific Time
You're lucky you can run it. I'm running Fusion drive on the iMac and according to some forums Big Sur and Monterey run like crap for speed. I'll sit back and run Catalina since I'm having no problems with it.
I too am on Catalina on my mid 2012 MacBook Pro and late 2013 Retina MacBook Pro. Is there really a reason to upgrade to Monterey? I got tired of chasing after MacOS updates. Microsoft stays with a new Windows for ten years before EOL.
I was OK with Big Sur on my iMac. Monterey isn't a huge upgrade I believe. Luckily I can change the desktop background picture back to Big Sur. There's no photograph for Monterey, just the ugly abstract 'art'.
I shudder to think. You're limited to what background you can use now with macOS. Apparently due to 'security' considerations. I hope this doesn't start to become a trend with other operating systems (I'm talking about you Ubuntu!).
You can change the desktop wallpaper but you're stuck with the default login screen. Believe me, I've tried changing it.
I hope they come up with a fix for changing it. Maybe I'm just getting to old for this modern day stuff like abstract art, if you can call it that.
I have not yet tried this myself: https://www.howtoisolve.com/how-to-change-the-login-screen-background-mac-macbook/ HTH - Please let us know if it works.
Prerequisite “FileVault is deactivated on your Mac” makes it a No-Go for me. I have seen even worse “solutions” though (permanently disabling SIP and other security measurements).