Should I create IAM role to allow AWS service send events to my default bus

For AWS Services, such as EC2, to publish events to your default event-bus, they do not need an IAM role. You get these AWS service events by default on your "default" event-bus - You do not need to do anything to receive them.

Please keep in mind, only AWS Services can do this on your default-event-bus. Other identities (users/roles), or other event-bus destinations require authentication to call the "PutEvents" EventBridge API.

Hope this helps!

Got it, thanks