You will need to be certified if you are a key appointment holder of a Comprehensive Licence employment agency (EA). This is regardless of whether you are involved in managing the EA or whether you perform EA work. Certification ensures that you have the relevant knowledge that is pertinent to an EA.
However, you will not need to be registered if you are a key appointment holder who does not perform EA work. You will still be held liable for any offence if you are found to be culpable.