I'm sure this has been covered before, but I didn't see it with a
quick search-- if you'll forgive a noob--

I've got a wet bathroom wall, tiled surround, outside wall. I've
pulled off some of the tile and backer board and the studs are also
wet/damp to different degrees, worst around the nails which were so
corroded they practically crumbled. There is roll-style insulation
with foil backing-- I can see by poking around the edges of it, that
the insulation is blackened and the outside wall has some black on it
too.

The studs don't appear to be badly rotted but it is softened. It's
worst around the nail holes, soft and black.

So if I pull out the insulation, spray down the walls with bleach, let
dry, then replace everything, does that seem adequate? Is there a
good test of how wet is "too" wet?