Same products you use at the sticks and bricks.. YES bleach (Concentrated straight from the bottle) is not good for the pipes and such.. Diluted with water (Rinse directly after cleaning) it is not so bad.. It's not the best thing for the black tank as it can put quits to biological activity but... Not that much bio-activity happens in the black tank anyway, I mean you dump too often.
I use scrubbing bubbles bathroom cleaner (or a generic equivalent). It's safe and effective on plastics, fiberglass, etc, as well as harder materials. Some of the generics are inferior cleaners, but others seem just as good as the real stuff.
For the toilet bowl, a brush and/or rag and water alone is sufficient in my opinion. It's not as though you'll be eating off of the toilet bowl, or having soap scum build up.
Use whats ever you use in your home. No it's not true bleach will harm the pipes. Bleach will not harm PVC at all. Bleach will kill the bacteria in your holding tanks and stop the break down of waste. That's all it will do.
The bleach will actually keep your pipes clean and keep algae from growing in there.
Dump some bleach in your drains to clear clogs. Been doing it for years and my entire home plumbing system is PVC.
If you just want to get rust out of the toilet, drop in one of the bleach tablets that you can get for your washing machine. Let sit in water for a while, when you flush it toilet is clean.