I have actually used google and nothing has come up so that's why i came here, and if anyone know's what would be the best case for custom WC system either Corsair Obsidian 800D Case or CoolerMaster Cosmos II Ultra Tower? and ill be running a 360 rad
Will depend on ambient temperatures how hot the CPU will get.
Though I suspect with that kit, your overclocking headroom will be limited by the quality of the chip and your overclocking knowledge before temperature will play a role.
Two D5's are absolutely not necessary unless you simply want to spend extra or plan on building a larger loop with more rads and blocks off this kit. Otherwise, the X20 750 pump is good for a CPU only loop or even adding a single GPU, DDC or D5 pumps would be suited for a larger loop. Dual pumps when you are considering CPU, 2+ rads, 2+ GPUs or you just want really good flow rates.