When you say "tank" the shower, that means the ceiling as well? Should that be set first?
You would have to check with local building regs, I can say that most professionally installed showers are meant to be flood tested, ie filled to the kerb with water and remain there for a period of time, (24hrs rings a bell somewhere, but could be way off, but a flood test nevertheless) whether your state insists in this, I do not know. And whether you would fall under those rules, again I am unsure.
I’m sure your local NTCA representative could advise.
But as we all know, DIY is one thing, professional is something else.
To answer your question tho...,,😁
The ceiling would only be tanked or tiles here if it was exceptionally low or it was at the clients request.
And yes, you would wait until the tanking is set before tiling.
There are several ways to achieve this.