BreOl72: I don't use Galaxy, so I guess, I have no horse in this race.
But..:
I also don't see the benefits of using a third party launcher, if there's an in-house launcher already available.
I use PlayNite. There are a lot of benefits of using PlayNite over Galaxy, and I would expect that it would be the same for those that use the Heroic Launcher...
1. I own several game bundles from itch, and the bulk of these games are not on GOG and therefore also not in Galaxy by default. Getting them into Galaxy means creating an account with Twitch just so that I can manually add them myself to the IGDB, waiting for it to be approved by the IGDB, then waiting up to 48 hours for it to show up in Galaxy.
2. I also own a bunch of compilation discs because hidden object games with silly plots are a bit of a guilty pleasure. Yea! Let's go investigating things I'm totally not qualified to be investigating, engage in numerous acts of breaking and entering, and go digging through junk piles full of rusty things. While a lot of these games are on the IGDB, the IGDB is under the delusion that they were not released on PC so I have to add the PC release information to make it show up in Galaxy because otherwise they don't. This means finding the game on the IGDB, making a change to show the PC release date information, waiting for the change to be approved, then waiting 48 hours for it to show up in Galaxy. In these cases, you have to also prove that the game was released on Windows PC by including a link to the game's mobygames listing in the changelog entry.
3. Even when a game does show up in the IGDB with all the proper info so that it can show up in Galaxy, it still won't show up in Galaxy if the title is too short. ᗢ is a delightful game where you play as a black cat and because the title is just one character, it won't show up in Galaxy. I've determined when I was using Galaxy that the title needs to be at least three characters long. For those games with very short titles, you have to find some other game to cannibalize so that it can appear in your Galaxy library, and the problem with doing this is that you can't update info in Galaxy to make it match up with the game you want to add because the data is being pulled off the IGDB.
4. If you don't agree with a game's listed genre, too bad for you if you use Galaxy. I consider Basements n' Basilisks, Behind the Frame: The Finest Scenery and South of the Circle to all all be visual novels. Yes, I'm well aware that none of these games are listed as visual novels on GOG because the developers/publishers don't want to market them as such. However when I go to play any of those games again, it will be entirely because I'm in the mood to play a visual novel. The genre isn't just people harems that the player is trying to get in bed with.
5. There's an arbitrary limit in Galaxy when it comes to cover and background art. Once you hit that limit, you're stuck with janky artwork and missing images.... or you can just start deleting games. That always works.
PlayNite doesn't make managing a game library feel like I have an unpaid job that involves helping manage the IGBD. If I want to manually add a game to my library, I can add it without having to turn to a third-party website. If I don't agree with the game genre that a developer wants to market their game as, I can list it as what I think it is. There's also no arbitrary limit on images that makes you stuck with missing and janky art. As of today, PlayNite is now prompting me to backup PlayNite metadata - which is another thing in its favor.
I'm sure that the Heroic Launcher is just as lovely but since I discovered PlayNite first, that's the one I use.