Did you used horticultural vinegar or household vinegar?* If you used the household vinegar and the weeds were established, that could be the reason you didn't see much results.
Yes, if you either surround your plants with it or puncture holes in the paper when you plant.* By the time the groundcover is mature enough to spread, the newspaper will have decomposed.
So the ground cover will still grow if I use newspaper in between and mulch?
Once it's established I guess I won't need the mulch anymore but for now.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.