Are you sure that's the case? I've already had the laptop repasted a month back as well with Gelid GC Extreme thermal paste, which helped the cpu temps drop from 95 tops to 80°C max, and gpu temps from 85-88 tops to 70°C max, however, the performance is basically similar to before.
Definitely the case, yes. CPUs tend to thermal throttle around 85C, with the aim of the throttling being to get the CPU down to around 80C. What you are describing is absolutely CPU throttling, and unsurprising that it is happening in Valorant, which is a CPU-heavy, poorly-optimised modern game that needs an absolute ton of CPU.
Although your laptop is classed as a "gaming" laptop, it still doesn't have enough CPU cooling to keep that CPU happy while gaming. AMD laptop CPUs run a lot hotter than their Intel equivalents, so although the Intel laptop in the video you linked to has a "worse" CPU than the CPU you have, in reality it runs a lot cooler and as such can run at max speed for longer without throttling than yours can. Ultimately the laptop in the video you linked would start throttling at some point if they ran games on it long enough, but it might take hours rather than minutes.
Surely my laptop can give similar performance?
It can, yes, provided you can keep it cool enough, which is very difficult on an AMD gaming laptop.
How much performance gain do you think I'll get if I install another 8gb ram 2400 MHz stick in my laptop to unlock dual channel memory?
A little. Maybe 3%? But anything you gain will disappear once the laptop starts thermal throttling again.
Maybe there are a few bios settings here n there which will help me (idk lol, just guessing)? If my laptop actually can't handle the temperatures, then that's a bummer.
No, there's no BIOS settings you can change other than underclocking the CPU, and most laptops don't allow this. You might be lucky and yours does. In which case I'd suggest reducing the CPU clock by about 20% and see if that helps. Definitely change your power plan to "Performance" or "Max" or whatever it's called, not "Balanced".
Your laptop can technically handle the temperatures, it does so by reducing the core clocks until the temps come down. Although as gamers this is never what we want to hear.
If you were to add additional cooling, eg a cooling pad, an external "blower" or maybe even an external liquid cooling solution, you'd probably find your performance stabilised a bit, but ultimately even with extra cooling the longer you play the hotter it gets, and since laptops are very small, compact and enclosed, there's not really anywhere for the heat to go.
One cooling "hack" is to run the laptop without the battery installed. The battery is responsible for generating and holding on to a lot of heat so if your laptop can run with the power adapter plugged in and the battery removed (most can) then you might find it runs cooler that way