Is the Conditional Card the best way to show an action on the Dashboard?

What should it say between 1.7-5W?

Regarding the dashboard, if you want to use a Heading card there is no need for a Conditional card, the Heading card includes a visibility option.

You may also want to take a look into Templating. It is one of the most powerful tools in Home Assistant for custom and/or dynamic values. There are community resources available that cover some of the basics of templating.