SCAR H is the best for long range IF you can handle that recoil
Well Im talking based on statistics. It has 2nd highest recoil next to the famas.Scar isn't really that difficult to handle. i find it to be among the easiest to handle however it has a little longer range than the ACE-23, but it also fires a lot slower.
Either of those twho weapons are a great pick for mid/long range combat.
When it comes to scopes i use either RDS+magnifier or an acog
For other attachments you should concider using attachments that increases your weapons stability as they make them more controlable
hope this helps
~xit