2. Wrong , Fitting a Water Block over GPU wont make it overnight OC champ.It will only give you a headroom regarding the amount of Volt's you can pump up while keeping temp's in respectable range.
3. I am using 2x Rx 480 Ref in CFX with fan profile @70 , which gives me 52-65*C range in almost all games at 1440P and all this on reference blower....i play Fallout4/ Doom/ Crysis3 .....I have benched both on custom BIOS with voltage unlocked @1.5V yet both remained under 85*C on full 100 fan profile , on WB i get 68-75*C range....So i will say you are wrong.
For better OC capabilities or Temp , you will either need Custom BIOS with AIB card or WB.
MSI Gaming X or Asus Strix is good AIB card.