I wouldn't say there are many drawbacks to playing this first. While there is continuity, the original Hypnagogia is pretty light on story, so there's not much that you need to know other than that Gogi is your friend.

I should probably mention that you don't need to have an account or launcher to get an itch game, you can just download the files from the website outright. (Edit: Though that might be a problem if you want to play on Steam Deck. Sorry, I wasn’t thinking about that.)

But word of warning: The original Hypnagogia doesn't have saves implemented, so make sure you have enough time set aside to play it in one go.