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)?