Still going through the thread, but I spotted a couple things to reply to.
FG&RP is still its own beast, but I do want to mention that freeforms seem to be more or less dead. Metric h*ckton of "Arms Race" games, whatever those are, and an active FEF community, but ye olde flood of Magic Girls games and whatever is a thing of the past. Mafia is a ghost town and the traditional forum games (of the player-above-you variety) are pretty quiet.
I can actually answer about the abundance of Arms Race games. They're basically team-based weapon design games. There aren't too many games in all honesty, they just have a disproportionate representation as you need one thread for each team in the game and typically have a third for the sake of having a place where players on opposing teams can chat with each other, frequently being a spot where the turns are placed as well. As a result of this need, having even 5 games running concurrently can explode into ~15 threads with a good chunk remaining fairly active.
Might be a good idea to shunt them off into a subforum to not strangle everything as a sideeffect, though there is a more optimum route in the form of a general subboard for 'team threads' for all competitive games using two (or more) teams of players to store their stuff rather than just one type of game. The neutral threads could remain in the main FG&RP, as the main problem is the subthreads used by the teams since they are greater in quantity and more active.
More than anything else I want threadmarks. It's hard to have a structured thread run long without it, and I don't even play forum games which I'm sure would benefit from it. Once you've spent some time with them the idea of not having them just comes off as senseless, and frankly I don't know what's going on with SMF that they're repeatedly breaking their search function instead of adding threadmarks.
As for the rest - you'd have to ask, I guess. But let's not pretend like SMF is elegant and minimalist, I mean look at this shit
What the duck did you just ducking say about me you little quack
What is this even for
Also you can email threads to people, which is either useless or harassment depending on what the end product looks like.
I think I remember having contacted Toady awhile back about implimenting these. He did seem to have some interest in implimenting them if their code was modified from Xenforo to work with SMF (they are an open source extension, so that is possible), but at the time I contacted him I seem to recall he was wanting to wait for SMF to become a bit more stable.