I don't think I'd use it for anything that can't be completely rinsed clean, like substrate etc. I have used it to soak a plastic tub before using it for fish and that was fine, but things like gravel would be a lot harder to rinse, unless you do it in small handfuls through a sieve or something like that. I don't know why you'd need to use it at all though, is there any reason or you just want to clean it? Hot water is all you need to use really
Bleach is very destructive. If you use it for gravel, maybe the gravel will look like it did when you bought it - fake. If I re-use gravel, I rinse it. If I am concerned about life in it, I rinse it in hot water.
Wood is destroyed in bleach. Rocks just need rinsing.
I'll use bleach on a bare tank, but not one with any decor. It is too toxic to play with, to me.
For plastic plants or glass castles etc, a mild solution madly rinsed would be safe. I hadn't thought of that, as a real plant aquarist, when I responded above. For organic or natural decor, I wouldn't use it - for porous wood, rocks or gravel.
If it's new just bought items, just a good rinse under hot water works.
If it's used, especially if it's from fish death from a disease like TB, bleach won't get all the bacteria from TB. Boiling the items in a full rolling boil pot for 10 minutes will work. If it's a lot of gravel that fills up a 12 quart stock pot, you will have to boil longer.
If decided to do a mild bleach bath on your items, I recommend a second bath in prime water or any dechloranater for a few hours to make sure you neutralize the chlorine in the bleach.
I'm old school, and I recommend boiling over chemicals any day.