Early Access to British submarines, global combat missions, a modified Domination mode, and a whole lot more! Read it on the portal
Hydro does detect submerged Submarines at proxy-spotting range (2km). Hybro detects out to normal ranges against Subs at Surface and Periscope Depths.
Multiple Battleships with 30mm Overmatch were banned to allow for greater amount of viable Cruiser choices. Also, the Louisiana was banned as she is still new enough to be worth giving her time to shake out first.
There are no banned Cruisers, but there several restricted ones due to the smaller team format. Tankiness is even stronger when there are less guns on the water to coordinate fire with.
Smaland was banned for overperformance in the mode. She was considered a mandatory pick so the ban allows for more DD options.
2 BBs provide cross-map fire as Battleship range is quite long. The inclusion of two major threats to Cruisers can cause a herding affect and lessen ability for dynamic movement.
Dropping to a single Battleship allows for more mobility in play, though it's reasonable to expect Stalingrad or other large-caliber Cruisers to be used as pocket Battleships for purposes of pinning fire.