Variable thermal absorption/dissipation with water cooling + Safety & reliability.

Hey, i'm thinking of opting for a fully water cooled solution for the next system. Namely the Scan 3XS X99 Cyclone SLI. But I have limited experience with water cooling setups, and none with a full loop that includes both the CPU and dual GPUs.

First question is what is the safety & reliability of full water cooling solutions like now a days, and is there any maintenance or up keep still required such as toping up the coolant reservoir etc.

Second question. I was basically wondering how does a water cooled setup handle variable thermal dissipation demand. Like for instance with my existing system, if I fire up a game that is putting my GPU under heavy load. I can just manually whack up the fan speed on the graphics card, in order to keep the temps under control. But how would a fully water cooled setup address such a sudden increased demand for thermal dissipation ? such as when you load up a highly graphically intensive app like a game.

Because with water cooling you can't very well force the coolant to become more conductive/absorptive ? or can you ?? The only thing I would assume you could do is adjust the fan speeds on the radiator. Is this basically the extent of the variability available with water cooling ? or are there options such as increasing coolant circulation speed and such like ?

Thanks

Also, if anyone has a 3XS X99 Cyclone WC system, I would be greatfull to hear your thoughts on it, as I can't seem to find any reviews of it other than the CustonPC one. Thx.