I'm not particularly interested in freelancing at this time, I have more than enough going on without giving you some unrealistic expectation. Most of what I was doing here was trying to make sure you weren't going to be scammed by people that talk the talk but can't or won't walk the walk.
Topic privacy however implemented is a massive task because it needs to be replicated throughout SMF, and there's a LOT of places that's the case. There was a patch that covered it in its entirety for SMF but its author will not be interested in sharing nor allow it to be reshared as it was implemented only for one site and to be used only as a base for implementing it solidly in one of the SMF forks. So far that work is on-going and incomplete and has shown many, many performance issues that can't always be perfectly solved and that performance must suffer to some degree to make it work, for mostly the same reasons the SMF team would advise to turn off post moderation.
For those wondering, it causes indexes to be less selective and less useful as a result; no point having an index for 1k rows when the only possible values are 0 and 1, the index doesn't really help you narrow down rows any.
It's a bit more involved when you have multiple options for privacy but the same problem occurs, it slows down anywhere that requires topic privacy to be implemented which offhand is board index, message index, thread view, posting, feeds, all aspects of moderation, and anything that is pulled by custom code or portals... and there's probably more in there that I can't remember right now. Even having exclusions like 'doesn't affect moderators' have a consequence for performance because you have to determine if the person is a moderator first or not, which all adds to the performance struggles.