Your questions apply to all the Rattrap games so if this sounds familiar, that's why.
Among the War parties is a supplement for Gloire. It adds natives, colonials, and explorers to the archetypes. You can play with as few as a single miniature per player or up to a half dozen using the rules fromt he books. If you add the squad rules that we have online, you could probably do 20 figures per side.
Standard game table is 2'x2' but you can do up to 4'x4' easily.
And the game works very well solo. The Encounter Marker system makes random events meaningful and they help propel the game forward as well as introduce new antagonists for the player.
I hope that helps a little.