Backup Catalina and restore to Mohave

Some weeks ago, I installed Catalina on my iMac (Retina 5K, 27-inch, Late 2014), but I'm unhappy with OSX 10.15 Apps are always freezing and sometimes the OS entirely freezes. I have to restart because of a freeze a few times each week. This morning I was unable to add a new contact to Contacts, and had to restart the machine before I could add it. This kind of thing never happened with previous versions of OSX. And it's just one of many ordinary operations that have frozen the machine or the app since installing Catalina.

An AppleCare support person I consulted at the time asked whether I had considered wiping the hard drive and reinstalling a Time Machine backup made when the OSX version was Mohave. Although I do a Time Machine backup once a week, I keep records on the computer and too much recent data would be lost be by reinstalling the weeks-old backup of OSX Mohave.

Can I do this though: I back up the iMac to iCloud. Then I reinstall the most recent Time Machine backup of Mohave. And then I download and repopulate just the data from the iCloud Catalina backup (Desktop, Documents, and Pictures folders). In other words, can I use this method to replace OSX Catalina with OSX Mohave on this iMac?