The 8565U has a TDP rating of 15W.
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Intel recommends to manufacturers that the long term turbo power limit should be set equal to the 15W TDP. Your screenshot shows that either you or Lenovo decided to set the turbo power limits to 51W. Maybe the engineer had dyslexia.
Your screenshot shows that once power consumption gets a hair over 30W, the cooling solution is already completely overwhelmed. Even with your undervolt, you are going to have a hard time getting maximum performance out of your CPU. It is very difficult to keep a CPU capable of drawing more than 50W cool in a small and light chassis.
Your goal of avoiding throttling is a noble goal but not a practical one. Running something simple like the TS Bench and you have already lost almost 700 MHz off of your CPU's rated performance. If you installed your motherboard and CPU in a desktop case and bolted on a desktop CPU cooler, you could run this test at 4100 MHz. Not a chance you will be able to do this in a laptop. There is no room in your laptop for the size of cooler that is necessary to provide proper cooling.
You bought a laptop with a 15W CPU. If you can run this CPU long term at 30W without it thermal throttling too much then I think that is more than fair. Your CPU undervolt is OK. Set your long term turbo power limit to about 30W. You can also leave it at 51W and just let your CPU thermal throttle when it needs to.
If you are going to undervolt the Intel GPU, you also need to undervolt the iGPU Unslice equally with the Intel GPU. The CPU core and cache do not have to be set equal to the Intel GPU.
Edit - Just read the specs for the Gen 8 Carbons.
10th Generation Intel® Core™ i7-10610U Processor with vPro™ (1.80 GHz, up to 4.90 GHz with Turbo Boost
4.90 GHz sounds amazing on the spec sheet but long term with a sustained load, a user will not be able to run their Carbon at any speed near that. Misleading advertising at its best.