The idea of overwhelming can make a very broad poetry topic. There are many things that can be written about the subject. Additionally, to describe the feeling and emotion, can sometimes require a lengthier poem (although often a short poem can get the point across).
When examining the idea of overwhelming as a poetry topic idea its concept can be viewed on a spectrum from things that have little meaning in a larger sense, but can still be overwhelming, to things that have a great deal of significance. For example, preparing for a party for two hundred people, with all the details, can be very overwhelming, however, in a larger sense, it may not be that significant. On the other hand, an illness, while not having many details, is more significant and can be overwhelming in a different sense.
Often a poet can use the poetry topic idea of overwhelming while actually experiencing the emotion. This can make for a poem with a lot of feeling. On the other hand, a poet in a relatively calm situation, can examine the idea of overwhelming from an outside perspective, and may come up with a poem with a different insight.
It could also be interesting for a poet to examine the idea of the stages in being overwhelmed. Interesting poems could be written about the start of the feeling and its end, in addition to examining the ongoing experience of the feeling.