As far as accuracy goes, it all depends on the shooter and wether or not the correct fundamentals are being applied. A good shooter applying the correct shooting fundamentals can be accurate with either platform. The Shadow 2 comes with a front fiber optic front sight vs the Tactical that comes with night sights. In my own personal opinion I prefer fiber optic, however im giving up being able to see it in all darkness, vs night sights, but with night sights its alot harder to have a good sight picture on far targets, and thats where the fiber optic comes out in front. The Tactical platform is close to the G17 size, but heavier. It all depends on you and what you like to carry. Your 3rd question goes back to fundamentals and what you’re trying to achieve at the range. Are you practicing self defense, or competition? And as far as the decocker question, with the Shadow 2 you can always bring the hammer down manually and have your 1st shot in DA/SA. That is not a big deal. Ive own both, and the Tactical has taken the backburner once i purchased my Shadow models.
My 2 cents