I don't know the names of some of the flowers or perennials, but I do know that perennials grow out and need thinned out after a period of time and in some cases it is every year that they would need thinned out, depending on what it is, and I am not familiar with Meadow sage or Dianthus, that I know of, lol. so no matter how far apart you plant them you will have to thin them out eventually, so pick a space that you want them to fit in and the bigger the space the longer you have to go and thin them out. They can be in the same bed but may require a thinning more so