So for a colony to last centuries in interstellar space with little to no prospect of resupply of any kind, you have to build in an awful lot of redundancy. You also need to cater for growth. You need a lot of infrastructure for long term care (eg hospitals). What you're building is living quarters for a thousand years over multiple generations.
But for a rogue planet you need far less. Consider the Moon. It has lava tubes. You can seal these, fill them with air and live in them. You don't need to accelerate that living space. Sure you still need to bring some things but it's far, far less.
What's more, if you have several such settlements in different lava tubes you have automatic redundancy. A single catastrophe won't snuff out the entire colony.
So for a true interstellar colony you really have to build a fleet because a single colony is too big of a failure mode.
A colony of fleshy biological creatures in an unsuspended form?
This seems silly. Even if intelligence remains biological (which I find exceedingly unlikely), then why wouldn't you just freeze them? That's a lot easier than moving a PLANET.
FYI - rodents can be frozen and revived. There's no fundamental reason you cannot freeze and thaw a human.
But for a rogue planet you need far less. Consider the Moon. It has lava tubes. You can seal these, fill them with air and live in them. You don't need to accelerate that living space. Sure you still need to bring some things but it's far, far less.
What's more, if you have several such settlements in different lava tubes you have automatic redundancy. A single catastrophe won't snuff out the entire colony.
So for a true interstellar colony you really have to build a fleet because a single colony is too big of a failure mode.