So unless you power off at the wall, the difference is 0.77 Watt. Compared to the power used during shutdown and boot up, it doesn't make much sense. They also don't boot up that quickly. And perhaps you forget something and how to boot it up/down more than once a day.
If you are away for an extended period, it makes sense. Perhaps even unplugging it from the wall, to also prevent harm from a power surge.
Still into the habit of not powering off, from when both Mac and very esp. Windows had terrible boot times. Turn on then come back in literally 5-10 minutes.
When family got their first iPads, had to show not to fully power off the devices whenever they set them down. ("No, it won't drain the battery if you leave it on...")
While I don't have an iMac, I do have a MacBook Pro 14" with the M3 Pro chip that is connected to the charger 24/7.
Is there any disadvantage to simply turning off the screen but not using Sleep mode when not using the laptop? When I'm going to bed, I just lock the laptop/screen and let the screen turn off. I don't close the lid (which would activate Sleep mode). Is there any harm in not using Sleep mode when not using the laptop (even when connected to the charger 24/7)?