Shutting down iMac or not

Hi there! You can restart your device once a while to free up cache memory. You can shut-down the MacBook incase you aren't going to use it in an immediate future. Apple MacBooks are built to handle Sleep-Wake action efficiently and hence if you are a regular user of the MacBook, you can simply put the MacBook to sleep. Trust this helps!

It's really a personal preference. It will not harm your Mac at all. It is generally a good idea to restart your Mac once in a while to free up any resources that may have been impacted by misbehaving programs and processes.

Personally, I leave my iMac on most of the time and to make sure there are no issues with bad/dirty power, I keep it connected to an Uninterruptible Battery Supply (UPS) to protect my expensive iMac from the dangers associated with dirty power. It is the primary contributor to failures of computers.

My iMac runs 24/7 and is only restarted for system updates.

I use auto shutdown and auto start up daily. Not a fan leaving any hardware on 24/7 unless required.

In preferences, energy saver and then schedule in the left side box.