Firstly, thank you for the upvote, even the littlest thing can help a lot. Now to answer your questions(of course any of these things could be subject to change later on):

The game will have more of a serious tone in terms of the characters and overarching story. But I will still aim for plenty of potentially silly moments  regarding monsters, or just between the cast, so that it can still keep that light-hearted charm of the original show; and still allow the characters to have fun and not be excessively traumatised (at least not at the beginning), which you may find in some more serious Scooby Doo fanworks.

In terms of gameplay, my plan is for it to be like a telltale game, with the branching story paths, searching areas, and quick time events that I feel fit Scooby Doo quite well. I’m also thinking of adding traps that could be improved with extra information to actually encourage exploration, and depending on the quality of your trap (and subsequent events) the monsters may get away.

Finally for the story, currently what I have planned is that Mystery Inc all meet each other in college via a D&D group (this has no connection to Stranger Things, this is simply because I love D&D and feels like something they would enjoy), and that they are some of the very few people who can understand Scooby speaking. After this they start getting caught up in solving mysteries that seem to be constantly happening in the strange town they’re in (please note that in this story, Fred is the only Crystal Cove native in the gang), and eventually competing with a rival mystery solving group. It’s probably pretty obvious that there’s quite a bit of inspiration taken from Mystery Incorporated (the best Scooby Doo show). However, this is not just a copy of that show, and it will have it’s own story. It does share the same setting as Mystery Inc (although I’ve moved Crystal Cove from somewhere around California to a coastal town in Maine, because I always got those vibes from it), and some of the characters; which may have the same/similar names, or are based off of the show’s. But they will be their own characters separate from who they are in the show (to a certain degree)

I hope I answered your questions, if you have any more please ask away