My immediate reaction (not being a physicist or an aeronautical engineer) is that I think it's unlikely you're going to see those kinds of performance character

My immediate reaction (not being a physicist or an aeronautical engineer) is that I think it's unlikely you're going to see those kinds of performance characteristics in something "propulsion" based. The first line of business would be the power source. The intuition would be that you need a mobile high energy power source. The counter-intuitive idea would be that the necessary power source would be so giant that it could never be mobile (like a dyson sphere), but there may be some method of linking a stationary power source with a mobile ship across vast distances. This offers control convenience if an advanced race still needs an authority structure and the possibility of remote monitoring. That also brings up the question of un"manned" exploration drone fleets bouncing between star systems and reporting back. As for movement, I would like to think that something with the observed extreme acceleration and the assumed interstellar capability is using a highly performant computer to calculate adjustments to an inside-out standing wave solution that the ship's outer shell is built for. Imagine shifting waveforms and your ship just kind of repositions yet it feels like you're completely still. Any space debris or other objects encountered while repositioning might get trapped outside the ship so that whenever you arrive at your destination you have to shed the debris. I'm sure a physicist will chime in and say this can never work, but at least from a naive perspective I like the idea of it.