If you are storing up to one value per topic, using a topic custom field may be better for this use case.
PluginStore is a simple KV store that is used to plugins where the cardinality of the data means it is a bad fit for existing custom fields tables. In the last years, we are moving plugins to their own tables to get better data reliability where it makes sense, like we did with the poll plugin. You can still use it if it makes sense for your use case.