Since the vSphere 5.5 or prior release only support 1 vCPU in FT . Most our critical infrastructure VM does have 1vCPU so that feature is not that useful.
Now vSphere 6.0 support for 4vCPU and 64GB RAM. so this will be real useful.
Now comes to your first question it will take the same amount of space since its a replica of first VM.