GHz doesn't matter anyways. In general nothing matters since threads can be individually throttled without you noticing (apart from declining performance). See my Lightsail review: https://www.karoly.io/amazon-lightsail-review-2018/
That depends on what you're paying for. If you're using Lightsail or one of the t-series EC2 instances you'll definitely get throttled as you don't get dedicated hardware. All other EC2 instance types give you dedicated hardware, on the Intel instances you get one hardware thread per vCPU and on the ARM instances you get a physical core. Those instance types don't throttle.
