The AB custom fan curve option is the cheapest and most obvious solution here. Well, it's not even really an issue because I've mentioned before 60C idle is perfectly OK. And the temperature differential between 55-62C involving your fan speeds is near negligent on both your GPU and fan lifespan.

If you're so inclined, you might want to go over to overclock.net and see if any custom BIOSes for your specific GPU that enables customizing your own fan curve without AB. Be warned that your remaining warranty will be voided if you do flash the BIOS and you're on your own since it's outside my knowledge.

Finally, you can also explore different options to permanently decrease idle temperature, but it's not going to directly solve this transitional region:

1. Installing more fans to better exploit airflow
2. Deshrouding your GPU and sticking on 2x120-240mm Noctua fans directly to the heatsink using some zip ties (or letting your bottom intakes doing the work)
3. Mod your current case to increase airflow by drilling holes in the front panel or reinstall your system in another high airflow case
4. Install an GPU cooling solution
5. Decreasing your ambient temperature using an air conditioner

Thanks Canuck_Cat. You've been very helpful.

Thank you for clarification, it raises even more questions however.
I'm using Norton Internet Security on some of my computers. Does it mean they are more insecure and they might even mine cryptocurrency right this moment? I mean maybe you know a good source where I can read how bad my situation is.

Just to add to this, the on-off fan for 55-62 degrees (or whatever it is) has been set to minimise power usage from the board and shouldn't have a material impact on the life of the silicon (it might reduce it slightly, but it would be offset by gains in the life of the fans, so net-net, no real difference).

It's probably only worth keeping your silicon temperature down at 30 if you have overheating or insufficient cooling/airflow elsewhere in the rig - or if its your personal preference.

From 2016:
https://www.computerworld.com/article/3089872/security-vulnerabilities-in-symantec-and-norton-as-bad-as-it-gets-warns-researcher.html

Lately there don't seem to be that much issues, found some articles from 2019 about Norton randomly crashing other applications like Chrome or preventing Windows updates as malware...

In general: Security software adds a lot of complexity to system - meaning even more bugs and holes. And they run at pretty high privileges (need to, in order to access everything on the system). Also they are notoriously bad - even with all their AI and heuristics nowadays - to detect and counter new threats and exploits. All those companies and institutions who got hit by stuff like Emotet, Wannacry, Hafnium, younameit had some form of security software. Sometimes the security software itself was the weak link (even simple Windows Defender had a severe problem at some point).
What they create though, is a false sense of security. "I'm protected, what can go wrong...". And that's why many security experts call those products "snake oil".
They do have their uses - if you download a lot of stuff from the web, and not brand new stuff, it's likely that the oldish malware that may come with it is known and found. But in this case an on-demand scan should be enough - no need to have the potentially vulnerable AV services running. The best protection against malware is still Brain 1.0, for everything else you need to rely on the OS and application developers to keep their products secure (yeah, MS... Hafnium... *sad laugh*).

About the mining - as I understood it, the new Norton products mine for you - so I guess you have to opt in and provide some credentials or something for you crypto-wallet. I don't actually think they do this on their own - if they did it would be real bad.