It is OK if you have done this deliberately. I just wanted to make sure that you were aware of this.
If I bought a laptop and the cooling was so poor that I could only run half the CPU at half of its rated speed, I would send it back to Lenovo and I would ask for all of my money back.
External cooling pads are not a fix for poorly designed laptops. Most people only see a difference of 1°C or 2°C when using a cooling pad.
Your turbo power limits are set to 30W and 44W. This is not realistic. Your cooling is struggling at 20W. I would suggest lowering your power limits to try and get slow and consistent performance. I would also suggest trying to replace the thermal paste to improve cooling.
You can infinitely try to juggle various ThrottleStop settings but this is not going to solve the cooling problem. Kind of like trying to find a band-aid when someone's arm just got ripped off.
Here is a look at the sorry looking heatsinks that Lenovo uses on their laptops with 15W CPUs. To say this is barely adequate is being generous. I think a U.S. penny has more copper in it than this heatsink does.