Difference in Internet Speed Cost

I currently have 400 MBPS Fast Internet. No gaming, no work from home, and only stream on occasion with a Roku setup. Not sure I need this much speed with only two of us in the house and usually only one of us on the internet. My question is would I miss the 400 mbps if i changed to 200 mbps plan and how much would it save me per month on the Xfinity Bill. Thanks for any help.