Yep, all working now on the front end. Even got those differences from the local to the remote server down to a single change on a file I rarely upload. But I clearly still do not understand RewriteCond. Googling for the exact problem I want to solve (do something different on local server) was able get what I wanted, but I don't know why my method was not working.

Specifically, I was trying to test if the URI contained a particular string. But either I was doing it wrong, or that's not possible. But It works, so I'm not complaining.

The URL for each individual post is
vp/ for viewpost.php.
someid/ for the post id
some-title-of-a-post which is just for show

Because the title portion is ignored, you can actually leave it out for a shorter link. Handy. But you'll still get redirected to the correct url by php.