Electric skateboards are not more dangerous than regular skateboards since the same skills are needed for both to ride well and safely. A lack of experience and skill will be a beginner’s problem. Just don’t panic when you are riding along or going faster than you can handle.
Speed wobbles can happen at higher speeds when the body is not ready for it. Going faster than 15 mph will cause these wobbles if the person is not strong enough to prevent wobbling with the ankles. Falling and banging the head on the ground can be the most dangerous thing to happen on a skateboard. Wearing a helmet can prevent significant issues.