Once again, I don't see why you would put posts for each forum in a separate table just for that forum. There is no DATABASE reason to do so. It will work just as well--and be easier to code--if there is only one table for all posts, no matter what forum.
So your choice to create a table per forum is your choice. I wouldn't do it. But, yet, it can be done. But once again that seems to me to be something that only an admin should be able to do and so it would be done from an admin web page using an admin connection. I see no reason to need to change connections once you get to the appropriate page.
But clearly you are designing your system completely differently than I would, so ultimately it is up to you.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.