The trajectory is more of the issue rather than the speed. You’d probably need onboard AI navigation to course correct and make landing spot decisions.

And don't forget that there's a "when". Planets ready to be seeded with life are rare at a given point in the universe's timeline. So the AI also needs to make course timing decisions in the magnitudes of 1B years...

It's so much easier to build and train AI then migrate our "humanity" into machines and just go from there to the Tannhäuser Gate and beyond.

When I was a kid, my dad, a very spiritual guy, after tucking me in, revealed to me: "Son, humans can already travel faster than light". My young and inquisitive scientific self said "What?? How?!?!" And he goes: "Just close your eyes and imagine yourself on Mars. It's instantaneous."

If you have AI, it can make the decision to "deploy" or loiter. If the technology is sufficiently advanced, it can wait a while. A long while.

Plus - why only one source of these capsules? Does only one mold cell in a colony generate a spore? Drake suggests that perhaps many will have done this same thing.

Nah, just aim your capsules along the galaxy with a speed low enough to not leave the galaxy.

The capsules will go around the galaxy, travelling through or oscillating above and below the galactic plane just like other stars.

Bonus 1: Make your capsules charged so they're guided by galactic magnetic field lines into star-forming nebula where a high density of stars are created letting them mix into protoplanetary disks.

Bonus 2: Just keep spewing out more capsules to increase mixing rates.