Photos

Yes, but if you are using iCloud to sync your devices, you will need to be careful. Because while you are syncing with iCloud deleting one on your mac will delete it also on your phone. Instead you might choose to select "optimise mac storage" which will then only keep small previews on your mac, taking much less storage.

You also have to ask yourself how you will get a backup of your photos if you are only keeping them on your phone.

How did you safe the photos on your iPhone? If you have not been using iCloud Photos and synced the the photos manually to the iPhone, you would have a hard time to get the photos back to your Mac, because the manual syncing is a one way route.

Increasing the iCloud subscription is a good idea to save storage on your Mac by using "Optimise Mac Storage", but you will still need a backup of your photos. your regular Time Machine backup cannot include the optimised items from your Photos Library.

I would copy the library to an external volume to have a backup of all photos, before you enable "Optimise Storage" and photos get removed from your Mac.

You're welcome 😊 Good Luck!