Are services like Norton 360 a good idea to install?

MacOS shares a lot of the lock-down mechanisms developed for the iPhone. Applications are all sand-boxed with a list of the resources they require, and they cannot ask for anything outside their sandbox without crashing. Signed Applications are checked that they are from legitimate Developers, and Notarized Applications are delivered with the assurance that they have NOT been modified since their release by the Developer.

From MacOS 11 Big Sur onward, the system is on a Separate, crypto-locked System Volume, which is not writeable using ordinary means. Any unauthorized changes to the crypto-locked volume are quickly detected and you are alerted.

So you could store just about every malware known to mankind on your Mac, and your Mac would not get infected spontaneously. Scanning for virus-like patterns might make you feel a little better now, but non-stop scanning is outdated nonsense, and a tremendous waste of resources.

Nothing can become Executable Unless/Until you supply your Admin password to "make it so".

It depends on whether you want to install the app for just an antivirus scan or if you need some extra tools the apps offer as well.

While macOS has built-in security features, third-party solutions offer enhanced protection and additional features that might be useful on its own. For example, if you need a VPN, password manager, or apps uninstaller.

Norton 360 Deluxe, in addition to antivirus protection, offers a two-way firewall, a password manager, and a VPN, making it a top choice for Mac users.

MacKeeper offers cleaning (apps uninstaller, duplicates finder), performance, and privacy features (VPN, ad blocker) in addition to antivirus protection.

Avast also has Wi-Fi Security Alerts, Email Shield( Scans incoming and outgoing emails), and a Real Site feature that prevents you from visiting fake websites.

Ptaxey--

You are speaking ONLY for yourself when you recommend that unnecessary junk.

The consensus here is that NONE of the items you mentioned are helpful in any way on a modern Mac.

Effective defenses against malware and ot… - Apple Community

Not in my opinion. See: macOS - Security - Apple

Protect your Mac from malware - Apple Support

and Set up your Mac to be secure - Apple Support

Also see this user tip:

Effective defenses against malware and ot… - Apple Community

+1