Welcome!
I have not experimented deeply in this area, but the consensus seems to be that smaller tips provide more english on the ball, so it's easier to get out of shape or throw the object ball when you don't mean to. That said, if you don't use extreme english, then the smaller tip probably won't change your game much. There are many posts here that discuss going to 12.5mm, 11.8, or smaller, and how that affected their shots.
The shaft construction, taper, tip, and other factors also influence the hit.
As to your other inquiry - I have a Predator Vantage shaft for sale. It is new. It has a larger tip size (12.9 mm) and a medium Predator tip. Many people like the Vantage for the stiff hit. I'm asking $265 shipped in CONUS with PP G&S. See the listing here:
https://forums.azbilliards.com/showt...31#post6718031
There's tons of good info on this site. Take a few hours and poke around.