Does an iPhone backup to MAC also backup Photos if iCloud photos is active?

No.

See the following from About backups for iOS devices - Apple Support

Backups from your computer

A computer backup of your device, which is not the same as a sync, includes almost all of your device's data and settings. A backup from a computer doesn't include:

• Content from the iTunes and App Stores, or PDFs downloaded directly to Apple Books
• Content synced from your Mac or PC, like imported MP3s or CDs, videos, books, and photos
• Data already synced and stored in iCloud, like iCloud Photos, iMessages, and text (SMS) and multimedia (MMS) messages
• Face ID or Touch ID settings
• Apple Pay information and settings
• Apple Mail data
• Activity, Health, and Keychain data (to back up this content, you'll need to use Encrypted Backup.)