I think project Deadelus is the correct route to take. I believe the Bussard ram jet was one of preferred propulsion systems after VASIMIR.
Like so many of these things, bigger really is better as long as you don’t have to heft it off the surface of the earth.
Cheap, for some values of cheap, and lots of redundancy.
And it gives us about 50 years to work out the tech to hear them when they get there.
/johnny
/johnny