Best Solution for Backing up my Mac

Buy an external HD such as a OWC Mercury Elite Pro and use that as your Time Machine drive. Please follow Apples instructions in :

https://support.apple.com/en-us/HT201250

iCloud is NOT a backup solution, please study what iCloud is for. Apple's suggested backup solution is using an external HD with Time Machine.

More to consider: Best practice for a desktop computer like the iMac, onr a notebook computer used as a dektop unit, is to use a desktop external drive. They usually have the more reliable 3.5-inch hard drives inside, and an independent power supply, also more reliable.

I use the ones that rkaufmann87 shows with his link, and have zero issues with backing his sage recommendation.

I buy the empty Elite Pro enclosures and install Western Digital Black-series bare drives. Takes only minutes. I have two Elite Pros serving my iMac. One Elite Pro has a 2TB drive for Time Machine to back up my 1TB Apple SSD. Some say that is too small but my TM drive is less than half-full yet has backups dating to April 2019—enough for my needs.

The second Elite Pro holds a 1TB drive that is for Carbon Copy Cloner bootable backups. Very handy should the internal drive fail.

NOTE: In the 2020 iMacs the SSDs are soldered to the logic board and cannot be removed for data recovery. If your logic board dies, so does the SSD and your data. Therefore it is mandatory to have a a local external backup with 2020 iMacs and 2016 and later MacBook Pros.

The Mercury Elite Pro drives are more expensive than the junk that goes on sale at office superstore every other weekend, but the pain eases when I ask, "How much is my data worth?"

I wholeheartedly agree with rkaufmann87's recommendations. I use the same OWC drive for my Time Machine and it's been extremely reliable. I use the 6 TB model due to the size and number of drives I'm backing up.

Good luck.