On Intel: For some mitigations disabling hyperthreading will disable them as some vulnerabilities are only present with it enabled. That being said, the overall

On Intel: For some mitigations disabling hyperthreading will disable them as some vulnerabilities are only present with it enabled. That being said, the overall performance impact will be greater from disabling hyperthreading than by enabling the mitigations (though some vulnerabilities remain so long as you don't disable hyperthreading). I wouldn't expect lower energy energy consumption from disabling hyperthreading: completing tasks faster allows the CPUs to reduce frequency faster.