FWIW, the shoes (and dresses) that were featured in Troian's slipper videos were the shoes (and dress/Abigail's dress/Sarah's dress) she wore to the ceremony and Queen's reception.
https://www.thesun.co.uk/fabulous/6...harry-meghan-markle-guests-wedding-reception/
I can't see Troian, Sarah Rafferty and Abigail Spencer all wearing the same dress to the evening reception, when everyone else changed.
One source of the "Suits cast didn't go to the evening party" story was that Jessica Mulroney's stylist posted some Instagram stories of an impromptu karaoke party at Coworth Park (which seems to have been the hotel of choice for most of the big name guests) that featured Rick Hoffman singing and what looked like Gabriel Macht on piano, during the evening.
I didn't see Sarah, Abigail, or Gina in those instagram story videos, so I can't speak to that, but it was definitely Rick singing.