Solar sail might help slow it down at destination + possibly a close solar Oberth maneuver to capture in an orbit in the target system.
Being a probe sized craft, deceleration as well as a very close flyby close to a star should be much more doable than with a big honking interstellar ark.
As for power - even a small nuclear reactor would be fine initially if it can last long enough for it to land somewhere suitable and start spamming solar panels. Then you are finally ready to get going on you first extra-solar Benchy. ;-)
Given that the payload would be tiny compared to a generation ship, I expect the powerplant would be able to get it there much faster.
> Solar sail or nuclear?
Solar sail won't work outside the solar system.
> How big would the payload be?
We cannot build it yet. But I expect the technology to do it seems possible.