Johnny's has two that I think might meet your needs: Easy Wave⢠Beachcomber Mix, and the Key Lime Parfait pellets. They both have reasonable heights, color, and controlled growht. Note that the Key Lime Parfait pellets actually have three seeds each: green, red and white, and are intended for easy basket preparation. Both of these are now on sale for reasonable prices at Johnny's.
Renais

Here is a link that might be useful: Key Lime Parfait

Easy Wave series would be a safe bet if you are looking for a bit of mounding habit on a trailing variety. Easy Wave pink in particular is very nice.

Also trialed Opera Supreme varieties this spring. Slightly less trailing habit than Easy Waves, but overall quite good, with a nice full mounded shape.

I grew operas a few years ago, and they were astounding and flew off the shelves. My fav wave for baskets have also been the easy waves, lavendar is especially nice. In twelve inch baskets,I usually put five plants for a quick fill, and particularly liked mixing the purples/lavendars. One tends to be more prostate than the other, and trailed better, with both in at the same time, it made for a good silhouette and a pleasing colour range.

Any Supertunia Petunia and especially Supertunia 'Mini' series. The best