The OnePlus 9 Pro has been shipping to people for about a week now, following its elaborate launch and extended marketing campaign. There are already countless complaints from people about their OnePlus 9 Pro handsets overheating, such as recording 4K videos or merely taking photos. OnePlus has already claimed that it is investigating the issue, but it is not a good start for the OnePlus 9 Pro.
https://www.notebookcheck.net/OnePlus-9-Pro-owners-complain-of-crippling-overheating-issues.531423.0.html
What one plus pro 9 they have mine works and performs flawlessly way better then the two brands you named above I own all three also you left out the rog phone 5 ect
Overheating issue affects the 8t as well. Camera and everything is sucky. 5g does not work. Although for overheating and slowness it's fixed by a MSM flash of the latest stable update from oneplus.
If this problem happens because of the OS software, that is definitely the OnePlus fault. But if it happens because of the chipset, I'm really worried if we might see Snapdragon 810 debacle all over again.