For the game specific forums, is there any way to organise them so you don't have to individually check out each one. Combining them with general discussion or something similar etc?

I don't believe so; though I suppose you could create a request for such a feature in the wishlist, and see whether it receives enough support for GOG's code monkeys to decide to implement it.

(It'd probably be a bit unwieldy, to be quite honest: especially if you follow dozens of games, and keeping in mind that a lot of those subforum threads have cryptic titles that assume you already know which game they're referencing.)

What you can do (assuming you haven't already) is uncheck the box for any game forum boards you're not interested in. Then you'll only have to check a given board for new content if its link is no longer grayed-out.

Having to do this has never bothered me; what does is the lack of a way to go directly to the first unread post. Your mileage may vary, and obviously does.

An alternative might be a way to make the listing dynamic, rather than alphabetical. That way, boards with new posts would jump to the top, the way their threads do, saving you the trouble of scrolling all the way down.