Framing is so subjective. Anything from no frame to ornate frame could work depending on the environment. But don’t let that scare you.
I love the simple solutions. For my looser compositions with white backgrounds, a straightforward white frame always looks good.
I found this modern profile frame at Target. The 16 x 20 inch size comes with an 11 x 14 mat. Which works for the Nasturtium paintings.
When my paintings have an edge, like the two winter paintings, a thin black frame pulls it all together. The photo shows the painting in a standard 11 x 14 inch frame with an 8x 10 window in the mat.
Dick Blick carries the Nielson Bainbridge line of frames, this is the black one I use. Super reasonable prices. Comes with UV glass, which you need for watercolors. Prevents fading. Although even with UV glass I recommend not hanging in direct sunlight.