Any games GOG is curating from Epic, these things need to be clear:
1. The base-game, its DLC's, and expansions should work offline fully period. This is NOT the case supposedly for Outer Worlds (source -
https://www.gog.com/forum/general/epic_store_games_you_can_play_without_the_epic_launcher/post258), so...this needs to be fixed IMHO for GOG to support/curate it/hand-pick it.
2. DRM should NOT be added later in Epic version's period. It should be DRM-FREE period.
3. If the DRM is known (Securom, Denuvo, etc) for Epic version, it should be stated on the page.
4. If the DRM is NOT know for Epic version, there should be a warning to the GOG user that Epic Games may or may not have DRM.
5. If a game-client is required to download the game and/or run in the background - this also should be noted. In Epic's case, they don't do downloading installers via web browser...so you will have to at least download their EGS Game-Client App.