Downgrading via backup of the same console: Yes, in fact it's by far the cleanest and most reliable way
Losing games/saves: If they weren't installed when you made the backup, they won't appear as installed due to missing tickets: however if the movable.sed is the same (you didn't factory reset/tinyformat/system transfer after creating that backup) you can just reinstall the tickets (or the cias with devmenu, which will see the files are already on SD and stop after the ticket)