It sounds to me like the word 'bleach' is being used for any product that lightens hair.
This is not really true.
Bleach is a chemical that does not have any pigments. It is mixed with a developer (peroxide + stabilizing chemicals), that opens the hair cuticle and lightens hair, exposing the underlying natural pigments which are generally a dark orange to pale yellow, depending on how long you leave the bleach on, and how powerful the developer is. Developer is graded by volume of peroxide.. 10 volume up to 40 volume.. The stronger the developer, the quicker it works and the farther it will go in lightening.
Some hair is so dark, it requires more than one application of bleach to bring it to a pale yellow. Sometimes the hair is too sensitive to get it to that level and it will not hold up to that kind of damage.
Toner is then applied to tone out the orangey or yellowey tones.
This is called a 2 step process for obvious reasons.
Permanent colour has chemicals in it that, when a developer (peroxide) is added, will lighten hair to a certain extent depending on the volume developer used. This product also contains artificial pigments which oxidize within the hair shaft and are permanently embedded in your hair. These pigments can eventually fall out or fade. Generally they will never come all the way out on their own, and permanent colour is not strong enough to remove them.
The general rule for when to use bleach and when to use colour:
First determine the number of levels of lift you want to achieve.
Use the swatches in the salon to find your natural level and look at the colour you want. If your dark blonde is about a level 7 (I am guessing) and you want level 9 highlights (really nice result) you will have 2 levels of lift you need.
To get 3 levels of lift or less, you can use permanent colour, with great results.
To get more than 3 levels of lift you need to use bleach unless you are a level 6, or a level 5 with fine hair.You can get 4 levels of lift with a hi-lift blonde in most professional colours.
High lift blonde is permanent colour that has boosted ability to lighten hair. I'm guessing most permanent lines probably have a hi-lift series.. The colour company I worked for had one. (Goldwell)
People with darker, coarser hair may not be able to get a full three levels of lift with permanent hair colour. The ability for hair to lift is based on texture and the natural level. Porous hair is really easy to lighten, whereas really shiny tight cuticle hair is very difficult.
With hair that is already blonde, there is NO WAY you need to use something as harsh as bleach!
Permanent colour will work great unless you have cuticle made of steel.
If the highlights go brassy after a while, you can use a toning mousse to drab out the gold. It won't damage your hair as all it has is pigments and conditioner in it.
I hope this helps.