I want to break my site down into multi 'Niche' websites. Can I do this with StagingPro?

Yes, you can. StagingPro will create as many environments as your license will allow. Use the Content and Design Migration settings to deselect the elements you do not want to move. By selecting the “Design and Content” and “Store Settings,” you will be creating an ‘Empty’ store with zero products but keeping the supporting store settings.