I think pretty much whenever, it’s more just about your preference of what’s easier to put on and off
My personal preference is when you start potty training, but do whatever works best for you and your family. "Rules" are meant to be broken.
I started my son in pull ups at 10 months old! They just work better for diaper changes for our family
We switched to the Pampers cruisers when he hit size 4 cause they were easier. The Pampers easy ups are literally the same thing, I don’t see a difference between them.
My girl had been in pull-ups since about 13-14 months because it was easier to have her just step into something vs. having to do the crocodile death roll every diaper change.