My understanding is that the Breakthrough Starshot approach intends to use a small RTG thermocouple of a few milligrams plutonium or americium, not solar. The optics are minimal and low resolution (~2 megapixel). The uplink is slow (~2 baud) — it’s basically reflecting a laser off its own sail. That’s still going to be optically better than anything you’ll get on or near Earth because you’re near the subject.
As for the time to accelerate, you may overestimate. Constant acceleration for months on end brings you to very high speeds indeed. If you’re accelerating at 1G a full year I think it’s closer to 0.9c than 0.2, I’d have to do the math to check.