Just to avoid any confusion, there is no “cloud” with Syncthing. The files can be stored and synced among multiple devices, but there is no central server or anything like that (which makes it different from services like Dropbox or Google Drive).
For the encryption, you cannot encrypt local files with Syncthing like you do with Cryptomator and such, but you can still use your operating system (or other 3rd party software) to do it, e.g. using BitLocker in Windows, etc.