It’s mandatory that you add your spouse to your application and return the COPR you were issued originally. Failing to do so is misrepresentation and will result in you never being able to sponsor your spouse for PR. So again, you have no choice. You are required to follow the process.
Yes, this will add significant processing time to your application since IRCC will now have to process all of the information related to your spouse. Pre-COVID-19, this normally caused around a four month delay. I don’t know what the processing is like now. But it’s certainly months.