@ian57 Very interesting article, thank you Ian !
My first attempt was OV=4, arm=1750, GPU=600. temp was below 51°.
So I decided to increase cpu and gpu to resp. 2000/750. But still OV=4. Big mistake, the RPi refused to initiate all the time, and impossible to recover the config.txt in W10. So I had to create a new system in my SDCard. No big deal, but I was pretty upset with me 
So I tried 6/2000/750 and it runs pretty fine with my Argon1 case so far, with pretty good temp (<55°C till now).
PSP games runs just fine now, except GoW, not very fluid. not a problem, will skip frames or decrease resolution for this game only.
the only cons is, from time to time, the RPIs refuses to start. the red led is there, but no signal to the TVset. Not a big issue, I restart everything and the 2nd time it starts well...
If I refer to the article, maybe an issue due to the GPU OC. I should try to decrease it to 700, or even less. Also it seems the OC of the GPU is not really useful/needed if I understand well. I also read benchmark results confirming this... I will investigate further...