As I said, Sabrett is definitely not kosher. Re: the others. I’d have to check the package to see if it includes the O/U “hechsher” (rabbinical certification) or the K, which does make a difference to some Jews. Glatt has a different/higher standard, and what you said about the sheep’s casing and where products are produced is correct.
My local ShopRite (Marlboro) sells Kosher deli at the regular deli counter in the back of the store (separate slicer and servers change gloves) but also has an entirely separate Glatt deli counter in the front near the Kosher products aisle.
In NYC, Katz’s is Kosher-style deli. 2nd Ave. Deli is Kosher (all Kosher products and no dairy), but Jews who are Glatt will not eat there because it isn’t closed on Shabbat.