How do Samsung apps get updated on Samsung devices?
Some are updated by a system OTA. Some others are either OTA-ed, or updated via Play Store. In total, they are updated in a moxed way of system OTAs and Play Store.

To be simple: Whatever you can find on the Play Store is updated via PS, and whatever else is shipped with an OTA.

I'm never a Samsung user but my friend has a Samsung, so I can only tell some of them (i.e. this list is incomplete):


Samsung Push Service
Samsung Browser
...And a built-in QR scanner (I forgot its name)