Powertop can, as far as I know, adjust some things - and make them permanent
via changes to config files.
Then comes the tlp service, if you have it active … and applies it’s configuration, overriding/changing the configured values.
You can use powertop to identify the points of interest and then configure tlp using that information.
That might be a flawed reading/report.
Or it may actually be true - depending on how the changing of the display brightness is implemented in the hardware.
(it may dim your display by wasting part of the energy through a resistor
the display brightness might change - but the consumed energy might not
… this is probably not the case - but possible )
I’m (still) using TLP
It was introduced and used by default in every new installation of Manjaro
years ago.
Some now may not have that active anymore.
But it was the default.
works just fine, too
Having two independent solutions
tlp and powertop
“messing” with power related configurations
at the same time
does not seem like a very bright idea to me
… as the two can evidently come to different “solutions”
kind of fighting with each other
making the result unpredictable
I have a thinkpad X1C6 wich has pretty similar hardware. At the time now I run only thermald and auto-cpufreq as a test and it’s working fine so far.
For power saving route with tlp installed, I would suggest this tutorial here in the forum.