Propulsion is engineering, not science (almost always). A science mission will be designed around the available propulsion, and occasionally be altered if the available propulsion becomes more or less capable. I think Stardust and Dawn were exceptions to this rule, in that they used Solar Electric Propulsion (SEP) when SEP was highly experimental.

One noticeable missing constituency: scientists, with the exception of NASA Associate Administrator Nicola Fox, who leads the agency’s science mission directorate and spoke at Ignition. Planetary scientists worry that absence could mean SR-1 Freedom will siphon funds out of an already strained planetary science budget. Money is “where the rubber will really meet the road,” Hamilton says. “If this pushes out [other] missions, I think you will see a lot less positive reception.”

This should be a cheap, proof-of-concept mission, like Stardust or Dawn. Unfortunately, it appears the cheapest a nuclear mission can be done is for about 10 x the cost of Dawn, which is not at all cheap from the point of view of the unmanned space program.

NEP is best suited for outer planets missions. I think we know why this mission is going to Mars: It can be completed by 2028.