Layering absolutely affects queue time and here is a link to a post directly from a blue:
https://us.forums.blizzard.com/en/wow/t/overcrowded-realm-update/255835
“Raising realm caps would simply forestall the problem, letting more players in at launch but creating an unsustainable situation down the line, with severe queues when we turn off layering permanently before Phase 2 of our content unlock plan.”