2 items:

#1 You can list the maximum number of work units to 6 by using the custom settings in the device settings. This would ensure you only get 6 and would not have any hyperthreading.
#2. You have a laptop. Laptops are notorious for having inadequate cooling, so even if they are capable of running flat out using all 12 threads, they tend to overheat due to not being engineered to run any length of time at full throttle. The problem is not the chip, but the laptop manufacturer not building the case or the cooling mechanism with adequate capacity for the chip performance over long periods of time, maybe as short as 15 to 20 minutes or less.
Not running any laptops, I will not offer any possible solutions. Perhaps others might. It would be helpful to know which model of laptop you have.

Cheers

Here is what I found using Boinc Manager only. I left the WCG profile setting at defaults.

On the Options/Computing preferences
At most use xxx % of CPUs: will control how many core/theads to use. On your 6/12 core/theads machine 50% would mean 6 WUs
At most use xxx % of CPU time: will control how much time the CPU will use. 50% would mean only process boinc 50% of the time.

So 100% and 50% respectively would mean process 12 WUs 50% of the time. I have no idea where your good settings would be.... and would this be as good as 50% and 100% respectively.

You can use HWiNFO (SpeedFan or other) to monitor the temperature.

I tried one of those gadgets with fans on the bottom you sit the laptop on and saw not much difference. They get power from USB so don't use the USB from the laptop.

The laptops I have are older 2/4 cores/threads so not really screamers.

This is your CPU:
https://www.cpubenchmark.net/cpu.php?cpu=AMD+Ryzen+5+5500U&id=4141

Try it my way. Leave the WCG setting at default.

Using Boinc Manager I just tried it now. Changing the "At most use xxx % of CPUs" to 50 and saving I saw the number of tasks drop from 4 to 2. Then 50 to 100 it went up to 4 again.

But if your way works then OK. If you have more than 1 device and they all use the same profile then the setting will apply to all.

Using Boinc Manager you can tune each device individually.

Either way should work equally well.

Cheers

You should be OK setting the number of processors to 6 and the processor usage percentage to 100%.

Default Profile settings
On multiprocessors, at most use: 6 processors
On multiprocessors, use: 100% of processors

Options/Computing preferences
Use at most 50 % of CPUs
Use at most 100% of CPU time

I have a i7-2600 Dell Optiplex (4C/8T, 4 units) and a Dell Inspiron i5-3330 (4C/4T, 2 units) set to 50% in Boinc Manager to keep the heat down.

Be aware your points production will be less than your previous FX-8370 system since you are running 6 units instead of 8 units at a time.