[Paul M]

The text is a phrase (most_visitors) so you could add bold tags to it, the trouble is that the count value would not be bold unless you left the closing tag off the phrase, but that would then screw up the names display. The only way you could fix that is to edit the plugin code.

As for the time, it uses whatever standard format you have set for your forum, to make it different to the rest of your forum would again require the plugin to be edited.