You can sync without record images.
Before you sync, be sure to review the settings. When you select a tree to "Download from Ancestry," the first pop-up window has an option "download citation media from ancestry." Uncheck that box, to prohibit census and other record images from downloading to your computer.
While you are there, I strongly recommend that you uncheck the box to synchronize automatically. Using Manual sync gives you much better control.
If you are uploading to ancestry.com from FTM, when you click on "Upload and Link to Ancestry" you will have options before you complete that, and you should review all of those options as well.