Combining photos in one iCloud account

Photos isn’t a part of family sharing , to share photos you have to create albums photo sharing but must be turn it on in iPhone settings photos , then the organizer in this case you can send an invitation to the others and they can see every photos that you can add to the album see the screenshot attachments from the second picture there is + symbol is where you can create your albums then invite others sending the request to their Apple ID in this case your wife can create albums and share them with you too

When you join family sharing a new shared library is created for the entire family to post pictures. You can add pictures there and all devices will "see" them. You can also elect to import shared pictures to either of your library.

You should have a family shared album and calendar. I don't know what the name is; probably something like family or shared, or similar. This if from the family sharing page:

When you set up your family, a shared album is created automatically in the Photos app on all family members’ devices. Everyone can add photos, videos, and comments to the album whenever they like and get notified when something new is added. Family Sharing also sets up a family calendar where everyone can view, add, or change events and appointments, and get an alert when something changes. And anyone can use the Reminders app to send time or location reminders to the family. So when it’s picture day, pizza night, or just a trip to the beach, everyone’s in the know.

They won't. Any pictures you take go straight to your individual library. You can then share with each other using a shared album. The alternative is to use one Apple ID for both of you (which isn't a best practice and has some cons). The advantage is that then you have one primary album. I have my folks set up that way as being grandparents they want all of the pictures between all devices immediately without having to do anything else. The cons are things like FindMy shared locations won't work properly, and everything is connected to one iCloud account.