I have a few TB iris and 3ft lillium between one bed of dls. I like to have early color with the iris the lilium bloom while the dls do. I may put a line of short annuals in front of that mixed bed. I have used marigold but might try begonias.
The marigold look nice up in the Fall till it freezes. I don't think deer like the smell which is a bonus!
The bed below is a mixed bed it has a bit of everything!