Did it affect game play?
Well yes, of course the ball bounces differently off a cushioned target, then plastic, and it sticks out a little so, it affects it in those ways.
I guess it depends whether you are a player that is very focused for tournaments, points, argues over angles...dont use target decals.
They serve to make the game look better, and nothing more, other than wear protection, but in home use.....
Can you peel off the backing with your fingers?
Yes, sometimes. I cant speak for the material in this specific batch, or even the heat in an airplane when mailed.
Nor can I account for the length of your finger nails, or manual dexterity.
Sometimes, you need to nick, with a sharp blade. Sometimes when you dont, you peel the print layer from the adhesive.