Back when I first asked, the answer to your clarification was “yes, both”. In my experience, a homebrew wiki that has characters, environments, people’s house rules, campaign ideas, new hacks, and the like is a very useful tool for RPG folks, and can serve as a community hub and reference hub with a very different purpose from a forum or Discord.
I’d generally recommend also posting things to the forum, but the thing about forums is that they are not designed for easy sorting. It’s great for the 1-2 weeks after you make a thing, but after that things sort of vanish. I can’t imagine how I would go about searching for hero characters here in a way that didn’t require me to sift through an awful lot of other posts, whereas a wiki that just had an entire page for them would let people quickly go and take a look.
I know how to build a wiki, and I’ve used Wikidot in the past to do so, but I don’t have the time to be a head editor on one these days. I’d be happy to be a contributer, though.