[Gravityloss]

There's basically four inputs to electric propulsion: power source mass efficiency (W/kg), required delta vee (m/s), required acceleration (m/s/s), and exhaust velocity (m/s). (Well there's efficiency too.)

You can approximately minimize total mass with this info. Turns out, your spacecraft will in total be heavier, if you go to higher exhaust velocities. You save on propellant but you need bigger solar arrays. Not worth it.

All this talk about "Mars in x days" assumes a fantastic power plant. It's a little bit like you're starting a car company and showing wheels and saying "my car company enables range and acceleration three times that of Tesla" while you don't have any kind of battery or motor yet.