1. Don't use quick disconnects, ever.
2. No. You can mix and match them, but not freely. There are several different flavors of metal used in water cooling:
Copper
Brass
Nickel-plated Copper
Aluminium (most likely to be found in a cheap radiator)
You cannot mix copper with aluminium, you'll get nasty corrosion. You'll end up with corrosion on a pure copper block as well, but it'll be much worse if there's an aluminum surface in there. If you want to avoid that corrosion, you must use pure ethylene-glycol (antifreeze), which doesn't cool quite as well as distilled water or most premixed coolants. I recommend seeking out components that have brass or nickel on the inner surface.