I don't want to see 100,000 photos on my iPhone.

To set up iCloud on your MacBook for syncing everything, including files, photos, contacts, calendars, and more, follow these steps:

1. Sign in to iCloud: Go to the Apple menu () in the top-left corner of your MacBook and select "System Preferences." In the System Preferences window, click on "Apple ID" or "iCloud" (depending on your macOS version). If you're not signed in, enter your Apple ID and password to log in.
2. Enable iCloud sync: In the iCloud preferences pane, you'll see a list of various apps and services that can be synced with iCloud. Ensure that the checkboxes next to the desired options are selected. For example, you can enable "iCloud Drive" to sync your files, "Photos" to sync your photo library, "Contacts," "Calendars," "Reminders," "Notes," and other options as per your preference.
3. Customize iCloud settings: Click on the "Options" button next to each app/service to access additional settings. For example, in the iCloud Drive options, you can choose to store Desktop and Documents folders in iCloud, or selectively enable syncing for specific apps. Explore the options and select the ones that suit your needs.
4. Sync preferences within apps: Many apps on your MacBook have their own iCloud sync settings. For example, in the Photos app, you can go to Photos > Preferences > iCloud and select "Download Originals to this Mac" to ensure all your photos are downloaded and synced. Check the preferences of other apps like Contacts, Calendars, Notes, and more to adjust their sync settings.
5. Monitor sync progress: After setting up iCloud sync, your MacBook will start syncing your data to iCloud. You can monitor the sync progress in the iCloud preferences pane or by checking the status icons in the menu bar. It may take some time, especially if you have a large amount of data to sync initially.

By following these steps, iCloud will sync your files, photos, contacts, calendars, and other data across your MacBook and other devices associated with your Apple ID, such as iPhones, iPads, and other Macs. Remember to keep your MacBook connected to the internet and ensure you have enough iCloud storage space to accommodate your data.

The syncing is all or nothing. However, these may help:

Manage your photo and video storage - Apple Support

You need not enable iCloud Photos on the phone.