No, they don't have exactly the same functions.
The difference lies not only in the material, but also in components such as the battery, housing and sensors.
As a rule, yes. Should this occur, the market price is likely to fall over time. As our daily prices are largely based on the market, it will most likely be possible to reflect this in the future.
According to my research, the GPS accuracy of the Epix Gen 2 is better than that of the Fenix 6S. Garmin is relying on a modern GNSS receiver for the Epix Gen 2. More modern GNSS receivers should also improve speed.