I just purchased an AirPort Time Capsule and set up backups of my OS X Sierra. (Actually, they're going to a USB drive connected to it but I think it amounts to the same thing.)
If leave for work with my laptop in the middle of a backup, will Time Machine handle that gracefully and do something sane or will it have a meltdown and corrupt the backup and all the other backups and become unusable?
Time Machine should handle this gracefully, with the in-progress backup continuing the next time you connect.
I have many many Time Machine backups that have all been done over wifi, and I have honestly paid no attention to whether or not backups are in progress or complete while taking my laptop in and out of the house.
Time machine backs up periodically. If you interrupt a backup (say your computer leaves the network during a backup) it will not complete, but your previous backups should remain in tact and it will resume the schedule when you are back. You can go into enter time machine and familiarize yourself with how it backs up over time.
