Bottles itself is great, but your running the windows version of GOG Galaxy in Bottles. So it can be a bit fussy at times.
Heroic runs on Linux. I have it from Flatpak. Linking it to my GOG account was easy. The UI is a little better to me and definitely more responsive. I can also pick custom versions of WINE or Proton on a game by game basis as well. With Bottles everything runs with a single runner. Hasn't been a problem yet, but it's a nice option.
The screenshot in the article shows Epic, GOG, Ubisoft and Origin so I guess it covers some library integrations beyond just GOG. But ya, not sure about Prime.