A sunny window is just fine. If you find the plant getting too long (stretching) you can always pinch it back a couple of times.

They wont get as big indoors, as they do outdoors, but a 5" round pot initially and maybe upgrade to a 8 or 10" round pot later.

Just make sure you use a well draining growing media, as soil tends to stay damper in winter. It is better to keep them on the dry side.

Funny you should mention accent impatiens. We had 3 flats of impatiens seeds (two accents and 1 tempo). The two accents damped off with a handful of plants remaining, whereas the tempo did a lot better. We re-did one flat with a mixture of various cultivars. The mosiac germinated 100% and the others about 75-80%... I think it is a coincidence, but you are starting to get me thinking about the accents !!!

The accent seeds I got from Parks had 100% germination. The accents I got elsewhere had less than 50% germination. I'd recommend getting them from Parks in the future. That's what I'm going to do.

You might want to move them to a less sunny window in summer or they will fry. They make great houseplants. They tend to grow more upright indoors and can reach 2' tall in time. You'll probably be pinching stems fairly often for your cuttings so yours won't get that big.

Some impatien seeds germinated in the pot of a houseplant we had on our deck last summer. They apparently seeded from a nearby impatien plant in another container. After we brought the houseplant back in the house for the winter, the impatiens continued to grow and flower all winter long. The plant is near a bright window. We plan to grow more impatiens as houseplants next winter.