Small overloaded functions can be used to turn reference into pointer:
template<typename T>
T * ptr(T & obj) { return &obj; } //turn reference into pointer!
template<typename T>
T * ptr(T * obj) { return obj; } //obj is already pointer, return it!
Now instead of doing this:
if(elem->Intersects(_bounds) == false) return false;
if(elem.Intersects(_bounds) == false) return false;
Do this:
if( ptr(elem)->Intersects(_bounds) == false) return false;
If elem is a reference, the first overload ptr will be selected, else the second will be selected. Both returns pointer, which means irrespective of what elem is in your code, the expression ptr(elem) will always be a pointer which you can use to invoke the member functions, as shown above.
Since ptr(elem) is pointer, which means checking it for nullptr be good idea:
if( ptr(elem) && (ptr(elem)->Intersects(_bounds) == false)) return false;