I need to permanently delete Bluetooth and Network drivers (Wi-Fi and Ethernet) from my MacBook Air running macOS High Sierra, so there will be no way to have any connection except the USB.
Is that possible to do from
csrutil and if yes, how?
Note: this is not a direct answer to your question, but provides some alternative points to investigate.
Within the strict definition of 'permanently', anything software is typically undoable with enough intention (e.g. boot from alternative media or operating system, or single user mode, reinstall or enable drivers, etc). Leaving USB accessible will not prevent a USB to ethernet adaptor or wireless adaptor from being installed given enough motivation.
Depending on the model of your MacBook, you may be able to pop the lid open and physically remove the wireless & Bluetooth adaptor. I suspect the ethernet will be soldered to the mainboard so hardware disabling might not be practical. Some non-conductive resin in the ethernet socket might solve that issue…but the USB to network adaptor will still be an available route.
To summarise, it depends on your interpretation of 'permanently', and to an extent the underlying reasons for wanting/needing to do this.