Hi there WJ-apple,
Thanks for joining us in Apple Support Communities! We understand you're asking if you can delete photos from your iPhone after saving them to iCloud Drive in order to make more device storage available on your iPhone. We're glad you're here, and we can provide some guidance.
To start, it looks like you have a considerable amount of iCloud storage available. Rather than using iCloud Drive to store your photos, we'd suggest setting up and using iCloud Photos with the Optimize iPhone Storage feature turned on. Have a look at these support articles to learn more:
Manage your photo and video storage
Set up and use iCloud Photos
We hope this information is helpful. Don’t hesitate to let us know if you have any more questions.
Cheers.