Hey there,
Welcome to the Forum
So there's possibly a few things going on. Firstly how old is the laptop? A few years? 2018/19?
Have you been keeping it clean? Disassembling, cleaning out fans etc? If you haven't done that yet, or regularly, I'd start there. After just 6 months, the fans and the exhaust vents will clog up with dust, grit, and what will eventually look like little hairs. When that happens the fans struggle to dissipate the heat, and this can cause additional throttling, on top of already temp throttling from the CPU.
Are the 80-90c temps at 3.6ghz or base (2.2)? Either way, although you're thinking your CPU isn't throttling, I'm afraid it is, and that's why it goes to base. Lets say it's 3.6ghz at 90c. Your CPU has a max temp of 100c (Tjunction) before it should throttle (at least that's how intel sets it). Most manufacturers set an offset on T junction to maybe 97c or even 95c in some cases. So when your CPU hits 90c at any clockspeed (that's pretty close to 95c), it will immediately dial back to prevent it from shutting down. The manufacturers use this offset, because often the cooling system (heatsink pipes/fans) aren't sufficient for the CPU they are using.
With all of that said, there are a few things you can do which can/may help.
1. Do as outlined above. Disassemble your laptop (there may be guides for it, so post your exact laptop model so we can check). Take out the fans and clean them with a can of compressed air. Do the same with the exhaust grid/frames with the compressed air. make sure all the dust is blown out and they are clean before putting them back. By cleaning them regularly, the airflow whilst the fans are spinning will be much better with the hot air escaping as it should.
2. Get a good laptop cooling pad. This will help with temps, and reduce temps by maybe 5-10c at idle, and maybe 3-5c gaming. Airflow is everything in a laptop. With the cooling pad raising the rear of the laptop, more cool air can flow through intakes on the bottom of the laptop. Cooler air then goes through the heatpipes and fans, and further cools the CPU. You can test this effect by simply lifting the back of your laptop up whilst a heavy task is running and compare when it's not raised. You most likely will see a difference straight away.
3. Consider whilst disassembling, replacing the thermal paste on both your CPU and GPU. Your GPU temps are on the high side, as are your CPU temps. Replacing the thermal paste with good quality paste will reduce your temps massively, by maybe up to 10-15c depending on which paste you use. This is not an easy task, but certainly doable with enough research. Knowing the laptop model will help here to get the right resource to help you.
4. Consider undervolting your CPU. To undervolt you can use Throttlestop or Intel XTU. Essentially, you are reducing the voltage going to the CPU, this has a number of positive effects. It reduces the temp of the CPU over all, this allows the CPU to boost to higher speeds and for longer periods, all the while your temps are lower than they normally would be! It takes some tricking around, but again there are lots of guides for it. This is just an example :
Undervolt i7 8750H with ThrottleStop - YouTube . TS is actually quite useful in many ways. It has a built in benchmark which pushes the CPU, and simultaneously you can watch the clock speed on the fly to see how it throttles.
Get back to us and fill in the blanks, and we can advise further.