As I mentioned
here, the 800 G4 and G5 Minis can accommodate 2 x M.2 NVMe SSDs and 1 x SATA HD (or SSD). In my G5 Mini HackMini8,1, I have 2 x WD SN750 500 GB M.2 NVMe SSDs and 1 x 2 TB SATA 6 HD (for Time Machine and backup). Before I apply any significant updates/upgrades to my production M.2 NVMe SSD, I clone to my second M.2 NVMe SSD (using Carbon Copy). This strategy has worked very well for me. I just performed a clone before applying the 11.6.1 update. Clone speeds are fantastic with this setup. It may seem like overkill, but if you rely on your rig for daily use and can't waste time recovering from a failed upgrade, this is a great strategy.
NOTE: After cloning a drive in the manner discussed above, the cloned volume will have a name identical to the original volume in OC's boot menu. Follow the instructions
here for changing the name of the cloned volume if you want it to have a unique name in OC's boot menu.
NOTE 2: I disable Time Machine on my cloned volume, so that if I do boot the cloned volume (e.g. for Monterey upgrade testing), my cloned volume isn't writing to my Time Machine.