As far as I know, SuSolid is the only plugin that can display you collisions between solid entities from different subgroups/subcomponents.
The Solid Intersection tool will make your model looks transparent and will show you intersections in solid green color with solid red edges,so very visible.It also has an intersection counter,so you know if there are some small intersections that maybe you can miss.
The plugin will also help you a lot to check and make all your components solid.