First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac. This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.
There are no known viruses, i.e. self propagating, for Macs. There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.
Anti Virus developers try to group all types as viruses into their ad campaigns of fear. They do a poor job of the detecting and isolating the adware and malware. Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.
If you believe you'd go some adware or malware there is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is desshoigned solely to seek out adware and known malware and remove it. The free version is more than adequate for most users.
Also, unless you're using a true VPN tunnel, such as between you and your employer, school or bank's servers, they are useless from a privacy standpoint. Read these two articles: Public VPN's are anything but private and Former Malware Distributor Kape Technologies Now Owns ExpressVPN, CyberGhost, Private Internet Access, Zenmate, and a Collection of VPN “Review” Websites.
Personally I shut down my iMac every night. The typical boot time in the AM is about 35 seconds so it's not an imposition. Booting often clears out temporary system and application caches and swap files. That is a good thing. Maybe once a month I'll leave it on all night so the routine maintenance processes can run.
Also keep at least a minimum of 50 GB of free space, more if possible, to help assure optimal system and application performance.
