Actually you can now get a family sharing plan! I was just looking at that. My wife and I both have 50GB plans, and I’m already GB of mine... mostly for photo and video all taken with iPhone 6. The iPhone X has higher resolution and 4K video capability, so that will eat up the storage at a faster rate. Looks cheaper to share one 200GB plan with her.
https://www.macrumors.com/how-to/icloud-family-storage-ios-11/
Oh... and you can reassure your wife that I don’t work for Apple.
Before I paid extra for the 50GB iCloud plan, I used Google Photos to backup my photos when I ran out of the free iCloud storage. Eventually I needed more iCloud storage for other iOS backup data as well since I also have an iPad and Apple Watch.