Sure thing bud.
Scope: Ballistic 40x (20x would work find too, just use one you like or are used to)
Barrel: No attachment/ flash hider ( the others wont help when using bi-pod/regular bolt)
Other: Range finder or 14x variable zoom (range finder max distance is 999m which kinda sux for super long range, but it can help dialing in the weapon)
Other: Bi-pod (keeps it realistic and fun, makes you a much better shot. You'll be more careful with the trigger and get better much quicker than the straight pull silliness)
So the 14x variable zoom can help with acquiring targets/shorter ranges as well as spotting which is critical for you team. I use the range finder because to spot and identify enemy snipers I use the PLD which works great. The best way to approach this is by finding good spots on the maps and pre-ranging your rifle. One way is to use the range finder and then zeroing your scope to the desired distance and keeping it constant, just like in real life. You make a mental or physical chart of places on the map and your mil-dot adjustment for that area. With netcode the way it is you need a stationary target most of the time. Another way is to use the ambush method where you place the round ahead of the target using prediction and essentially have the target placing himself in front of it on his own. Like leading a target, this is hard now because netcode updates your screen at about 10fps while your prolly running 60+fps and at those distances it get very jerky/ rubber-bandy so stationary targets is where its at.
Another thing that makes it more fun and effective is to work with a team. A spotter/co-marksman is a huge advantage, they help acquire targets and can help defend against counter snipers. One person can roll with a long range setup and the other a shorter range scope to aid with tunnel vision and other threats. The 2 man element is ideal. They can also help you dial the rifle in, letting you know if your high or low and by how much if you need to re-chamber a round fast. This is also super fun with a buddy of course.
Here is an older video that is more long range based with many shots way past the range finders capabilities. I know this post is longer than what you probably wanted to know but it was fun putting this stuff in writing.