I'm using Engine Ice myself.
Besides being non-toxic (propylene glycol based), it also doesn't become acidic over time as the ethylene glycol based coolant does.
It also doesn't have additives that can damage water pump seals.
Engine Ice comes pre-mixed 50/50 with deionized water in 1/2 gallon containers.
Now if your racing, then some tracks only allow water, but some may also allow Water Wetter. It's a coolant, but not an anti-freeze as Engine Ice is.
Regardless of which choice, the ideal water to use is deionized water, followed by distilled water. Use tap water only if you have no recourse.
Deionized water is chemically pure water with absolutely no trace minerals.
Distilled water still has some trace minerals and tap water can have tons of dissolved minerals that can wreck havoc with your cooling system.