My question is rather simple;
Does the alignas specifier work with 'new'? That is, if a struct is defined to be aligned, will it be aligned when allocated with new?
Before C++17, if your type's alignment is not over-aligned, then yes, the default new will work. "Over-aligned" means that the alignment you specify in alignas is greater than alignof(std::max_align_t). The default new will work with non-over-aligned types more or less by accident; the default memory allocator will always allocate memory with an alignment equal to alignof(std::max_align_t).
If your type's alignment is over-aligned however, your out of luck. Neither the default new, nor any global new operator you write, will be able to even know the alignment required of the type, let alone allocate memory appropriate to it. The only way to help this case is to overload the class's operator new, which will be able to query the class's alignment with alignof.
Of course, this won't be useful if that class is used as the member of another class. Not unless that other class also overloads operator new. So something as simple as new pair<over_aligned, int>() won't work.
C++17 adds a number of memory allocators which are given the alignment of the type being used. These allocators are used specifically for over-aligned types (or more specifically, new-extended over-aligned types). So new pair<over_aligned, int>() will work in C++17.
Of course, this only works to the extent that the allocator handles over-aligned types.