iCloud & iCloud Photos · iCloud Drive basics
Can I use iCloud Drive without iCloud Photos, or the other way round?
Short answer: Yes — they're separate switches in System Settings → your name → iCloud. Sync files without photos, or photos without files; whichever you turn on shares the same iCloud storage.
Yes. They're independent switches in System Settings → your name → iCloud. You can sync files with iCloud Drive and keep your photo library local (backed up another way), or sync photos while keeping files off iCloud. Both share the same iCloud storage when on.
Choose by what you need on other devices. For how they differ, see iCloud Drive vs iCloud Photos.