How lovely! They look like cuttings. I grow some impatiens from seeds this year. I have the pricy mixed-color double Carousel. It seems to me that they grow slower and weaker. However, they branch themselves without my pinching. At this time, each plant have 2 pairs of true leaves.

First of all, your impatiens look wonderful! If you decide to pinch them back, check out the plant propagation forum and search for "Pinching & Poking Annuals" by paulinep. She has a useful link on How to Propagate Impatiens and Coleus. You'll end up with a bunch of new plants!
Chris

I wouldn't pinch them back just yet, wait until you get them in the ground, then pinch away! Also, I have not had much luck pinching the New Guinea Impatiens, so you might want to refrain from using this methoc on them.
Your seedlings look terrific, before long, you can have hundreds of em. Be sure to check out my albums and see my beautiful impatiens that reseed in the crack between my cement (faux brick) patio and the real brick wall. I treausre this little surprise garden when it returns each year--even wiggle out many seedlings to plant elsehwere when they get too crowded. Ya gotta love these plants, I have some blooming now, we have had such a mild winter here, even had a blossom or two this winter.
Pauline

Here is a link that might be useful: All of my picture Albums,