iPhone not enough space for backup

Hi Apple Community,

I recently went from an iPhone 7 128GB to an iPhone X 64GB.

I backed up my iPhone 7 to my computer (I don't use iCloud) and turned in my iPhone 7 to T-Mobile (Jump on Demand program) and now have the iPhone X.

When I tried to backup, I got the error message that I didn't have enough space on my iPhone X.

I am short about ~700mb. My iPhone X has nothing on it - only the ~6gb iOS and apps that come with the phone.

Is there a way I can select what is backed up from my iPhone 7 back up file?

After a couple hours of research, I saw that there are 3rd party programs that advertise that you can do this but I first wanted to ask the community if there is another solution?

Thank you for all your help!