For toilet bowl cleaner, you want to make sure it has the ‘quality seal’ on the packaging. It looks like this.
Generally, if you have hard water and a lot of issues with limescale, you will need an acidic cleaner. These are usually advertised accordingly. Bleach won’t help with limescale and is usually not necessary. It’s also very dangerous to mix bleach with acidic cleaners.
However, I find it much easier to check if the given answer is correct, instead of having to find the answer myself.