@Saoiray ok, I think we could say that the problem is solved!
I changed the default selection of the graphics for Brave, adjusting it to make it similar to edge, chrome etc. (integrated intel graphics) and… no more throttling! It was a problem related to the configuration of 3d settings.
I did a few tests with brave only and then with edge etc, no more overheating.
What can I say… Thank you very much!!! I am really grateful to you and @Mattches for your help! 