Yes, EMP attack is a new type of warfare tool that powerful countries can use for forthcoming battles. Many sources also claim that China has already used EMP technology against India, and Mumbai’s blackout is a result of its attack. However, if I address your question, then yes, an EMP attack can damage electric grids and electronic devices if the attackers enhance the voltage supply.
If we talk about what will work after an EMP attack, then yes, satellite phones and walkie-talkies would work after an EMP attack for communication purpose. You can also read more about it from our this article https://peektimes.com/survive-an-emp-attack-2021/. Similarly, if you have installed a solar system in house for power generation, then it could also be very beneficial for you. Your electricity supply wouldn’t be hurt in that case.
But it is still a dangerous situation because if planes’ air control communication is hurt, they can come to the ground free fall. It is serious concerns, and countries like the US etc., are already working to stop such EMP attacks in advance.