I know there are many discussions about this topic, but I wanted to make sure the general knowledge applies to my situation:

2nd floor Bathtub/Shower are located against an exterior wall. Wall is as follows: 2 thick Brick, Wood nailer strips, lath, plaster has been removed. I put up a new 2x4 stud wall over the lath because there wasn't enough room for pipes between the lath and brick. Also figured I have more room to pack in insulation. My idea here is to shoot a bunch of great stuff behind the lath then put a piece of drywall over the lath/between the studs. Now we're in the stud wall, I've got my pipes and such, and can stuff the pink insulation in and around them, then cement board/tile.

In my mind I've got a lot of insulation in that space. Seem like enough? Also have an air duct nearby in the floor and could send hot air up the stud cavity... Thoughts?

insulate between the pipe and the outside/cold

leave as much piping as possible exposed to interior temperature

In other words; insulate BEHIND the piping, very little if any on the drywall side

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

also, which exposure does the wall face. north is far more dangerous than south..

Put pipe insulation over both hot and cold pipes first and make sure the seams and joints are sealed. The pipes should be as close to the sheetrock as possible. Then insulate on the backside (exterior wall side ) of the pipes. The 'deader' you make the stud cavity, the better your chances will be.

Wall faces east