OK, I downgraded the BIOS to v1.60 -> The computer still crashes at login.
Then I removed the cpu, sprayed a little of dry air of the socket and the cpu, remounted everything -> The computer still crashes at login.
I do have another computer running on Windows with I5-8400. So i took some time and swaped the cpus.
-> The Windows computer seems to work OK with the I7-8700.
-> The High Sierra one no more crashes at login =).
I would be interested to know if this kind of behavior is normal or surprising.
Anyway, I think I'm gonna stick like that for now. Thanks Erik for the guide the Clover folder.