Just want to share that what i did.

Surface pro 3: I upgrade the windows pro 8.1 oem to windows 10 pro with no problem, and ensure the windows successfully activated
And then I get the ISO from windows website, and do a clean install directly using that ISO and once login to windows 10 pro and connected to Internet, it showing windows activated.

Msi gt70 2od: this computer come with windows 8.1 single language oem , and then I got the retail windows 8.1 pro key from student offer and has been used in this computer. When prompted to upgrade to windows 10 , with no problem as well, it showing activated.
After that I use the same ISO from Microsoft to perform clean install, but this computer cannot be activated under windows 10 pro, however I still manage to activate the windows if I upgrade to windows 10 from windows 8.1 pro

So I'm thinking that, if the laptop perform clean install of windows 10, it will read the key form bios (oem single license) and store somewhere in windows 10. Once I connected to Internet and doing activation, it will fail as previously the windows activated with combination of hardware I'd + windows 8.1 pro key

I still got one desktop with windows 8.1 pro since I assembly it, I think should have no problem to do clean install, as the motherboard don't have any oem key has been set in it.

i used msi for almost 2 weeks after upgraded to windows 10 pro, that weird...