Specialist bug removers are really just a money spinner, I am afraid. There are two types of product sold this way:
Solvent based product- typically these are sold as bug and tar removers. They are not water dilutable. They will be very effective with bugs and much much better on tar than option 2. Unfortunately, because they cannot be diluted and are necessarily 100% active products, they are really quite expensive.
Water based product - These will be water dilutable and will be much much less than 100% active so are much cheaper than solvent products. Against bugs they can still be very effective but against tar they will be of limited use and often totally useless.
The water based products are often very similar to APCs, there is very little special about them. Likewise, very similar to prewash products. In some cases, bug removers are actually 'ready for use' versions of APCs - they are diluted yet strangely cost more than many of the concentrated APCs out there!