My opinion(s) - - ->
You can never have enough magnification. As long as you do not go ABOVE 8X on the low end. For several years I shot 600-1000yds using a Leupold 8-25X50. I really could have used another 10X or so.
Your scope MUST have the third turret. (On a good quality scope you can use it for rangeing also.) It MUST have target turrets easy resetable to "zero".
Since my long range days I have bought several first focal plane scopes. For some applications I love them. What most people do not consider is that you can change the size of the duplex. I really like this "added bonus".
Choose your reticle wisely. Consider most all of them. Some are extremely "busy".
For the longer ranges you will need to add a bubble level to your scope. If your scope is canted just a couple of degrees,at 1000yds it will make a difference.
Buy the absolute best quality scope that you can afford. A great shooting gun is nothing without a quality scope. --- SAWMAN