A dapper chap without a doubt
Depends on what you're powering. If all you need is long term propulsion and life support, it might be plenty. (Especially if you swap it for an annie plant.)Planetary cores are not meaningful power sources by the standards in play.
Even actual spontaneously formed planets do hold themselves together well enough to be useful.I think there's very good reasons to think that having bits that are able to hold themselves together remains important to Schlock Mercenary tech, even for precursors.