Some Linux distros uses cupfrequtils to control CPU dynamic frequency scaling. This makes the processor run at lower speeds when demands on the CPU are lower and boosts the speed up to the maximum when it's under a higher load. This is so the CPU will generate less heat and consume less power. The default CPU governor used by this utility is "ondemand" which is the best compromise between cooling/power consumption and performance. Other available governors include performance and conservative. Run
to see all available governors on your system. Performance causes the CPU to operate at higher frequencies even though the load on it isn't that heavy, while conservative basically slows down the changes between frequencies: ondemand switches to a higher frequency briefly when there's a short spike in processor utilization but conservative tends to delay that switch for a moment in case that load quickly decreases.
MX Linux uses this but it is by terminal only - I do not know of any Linux OS that has it in the panel by design
There used to be a couple of gui’s for cpufreq.
One was a desktop widget for KDE 4. But I don’t think it got ported to KDE 5.
The other was a system tray widget that you could use in any desktop. Once you installed it, it auto-ran when you logged into a desktop session, leaving an icon in the system tray, which you could click on, to set your options. But I can’t remember what it was called.
Both of them let you select settings for cpufreq. Settings would persist/carry over to the next desktop session.