What type of chili in Olive Garden ‘Calabrian Chicken’
Calabrians eat a lot of chile peppers, but usually the one referred to as "Calabrian chiles" to foreign audiences is a variety of diamante chile pepper, grown in Southern Italy, salted and packed in oil, and sold as "hot long chile peppers".  These are commercially available in the USA from brands like Tutto Calabria and DeLallo.

The confusion comes in because the residents of Calabria province like a lot of peppers, and various other peppers are grown there, and even packaged and exported.

Calabrian chili peppers are not pepperoncini, or at least not what is sold in the USA as "pepperoncini". Those are a variety of small chile pepper, bred from the Anaheim, grown in the USA, picked green, and sold pickled.  They would be a terrible substitute.  Where you probably got that recommendation is that the word "pepperoncini" is Italian for "hot peppers", generically.

As for growing them, I'm not sure what to recommend.  The name they go by in Italy, "Diamante" after the town where they are grown, is used by several completely unrelated pepper varieties from English-speaking seed catalogs.  So I don't know what that pepper would be named if you wanted to plant it.