Here’s one approach.
Untitled.xcf (89.4 KB)
Using the Text tool, type out the text in the size and color you want for the body of the letters.
Duplicate the layer. Turn off that layer’s visibility. On the first(lower) layer, use select by color. Grow the selection.
Use the Bucket fill tool to add the edge color. Turn off the selection(Select None). Blur that layer if you wish. Turn on the visibility of the top layer.
Hope this helps.