Technically speaking you won´t need an aftermarket CPU cooler, because your CPU can´t be overclocked.
However, if you live in a hot location, or your case has not a good air flow, or any issue regarding to temps, then it is a good idea to get a CPU cooler.
Hyper 212 Plus and EVO are basically the same, but with a few differences -- basically the fan in EVO fits better than the Plus. So, the EVO is better.
As for for an additional fan, it is not really necessary, tough if you place one you will get around 3~5 less degrees.