2-ethylhexylacetate is an oil soluble liquid. It is not, I believe, used in DexCool It is a solvent and would have a limited application as a plasticizer. We used to use it to dissolve very special compounds which wouldnt dissolve in much of anything else. It would certainly damage elastomeric seals, etc, if it were used in DexCool. It wouldn't be soluble in water.
I suspect your 2-EHA may be 2-ethylhexanoic acid .It IS one of the Organic Acids which is patented to use in OAT technology. It would be used as the neutralized salt, not the acid form.
Common plasticizers are usually things like 2-ethylhexyladipate or di-2-ethylhexylphthalate.These are added to plastics (like dashboards, etc) to keep them soft and pliant. When they cook out of the elastomer, this is that oily film you see on the inside of the windshield.