Re: Remington Nickel Plated Brass
I've seen a few posts that say "don't go there" for rifle.
Pistol: The reason why many top IPSC/USPSA shooters use nickel plated brass is usually said for the increased lubricity. In double-stack magazines (STI/SV/Para/Tang) there may be some slight benefit. I've used both and don't have a strong preference. I definitely get more split cases after less reloadings with nickel plated (Starline & Armscor).
Rifle: In my case, I neck turn all my LR brass so the nickel plated stuff didn't make sense. I figured I'd be turning a good amount of the plating off the neck. FWIW, I can't say I've seen nickel plated rifle brass being used in competition.
"The common choice is Lapua, is that because it offers the most accuracy or because you can reload it more times?"
General consensus is Lapua has tighter tolerances, more uniform, and is harder brass than Rem. These factors would affect accuracy and longevity.