That might explain your misting-up problem. Sometimes, the drain holes can be hard to find.
Re. antifreeze, it is all still ethylene glycol. The "IAT / OAT" thing is just the additive package for corrosion protection and lubrication. Generally, the older OAT stuff is blue, but IAT stuff can be any colour. OAT will work in any engine, but only lasts a couple of years and then (in theory) should be replaced. IAT lasts longer (up to 10 years with some formulations), but can attack "yellow metal" (which really means anything with copper in it). So if you have brass sensors, bleed plugs, etc, or copper radiator core, end tanks, heater matrix, etc, then you shouldn't use IAT.
Re. antifreeze, it is all still ethylene glycol. The "IAT / OAT" thing is just the additive package for corrosion protection and lubrication. Generally, the older OAT stuff is blue, but IAT stuff can be any colour. OAT will work in any engine, but only lasts a couple of years and then (in theory) should be replaced. IAT lasts longer (up to 10 years with some formulations), but can attack "yellow metal" (which really means anything with copper in it). So if you have brass sensors, bleed plugs, etc, or copper radiator core, end tanks, heater matrix, etc, then you shouldn't use IAT.