The Nintendo Switch version of the Doom Eternal is finally arriving next week on Tuesday, December 8. The release will be digital-only, though, and available through the Nintendo Switch eShop and digital codes from other retailers. According to Bethesda's FAQ for the game, those who pre-ordered the game may have their orders cancelled. You could reach out to your retailer if your order got cancelled. Doom Eternal's storage size is 18.8GB. Its The Ancient Gods: Part One downloadable content will be available at "a later date."
Source: Polygon