Which to choose: Rosemary (might it not be hardy enough, how wide/big will it get), Veronica (Speedwell) too bushy or will it get TALL ENOUGH, or Hydrangea (may not bloom, to big, pests. etc.)?

LOCATION SITE: hillside, morning sun, near an oak tree (about five feet from the trunk, but still under the low hanging edge of the canopy). In the back of a bed directly behind (within 2 feet) of a row of peonies. (I want it big enough to be seen from behind the peonies but not tall enough to have to worry about the tree, or so wide it crowds the peonies.)

CONSIDERATION FACTORS: Ease of care, no work, no pests. Nothing invasive. I want to plant it water it with the lawn -- that's it. Although the options I listed look and grow differently from each other, I do want it to look nice....nice foliage, blooms, flowers, etc

MAX SIZE: 3x3. If I do the hydrangea I'm leaning toward the Pia. Seems to be the best choice size-wise.
So I'd say right now it's Hydrangea first choice if you all say it would work, rosemary second, Veronica (speedwell) third. I don't like the look of it as much. Plus it may be too short. (Also thought about and ruled out phlox becuase I read about pest/diseases it's subject to. But like the look of them as long as they don't spread.)

Or should I just plant more peonies (or daylillies which are already there too, in the in front of the peonies).

On one hand I want to try something different, more variety in the planting bed - and I do like hydrangea or rosemary -- on the other hand I could go with what I know works.