For insects, a longer macro lens is usually preferred because it gives more working distance at the same magnification, which helps avoid scaring the subject.

That’s why a 150mm or 180mm macro is often favored over a 90–105mm macro for insects. A 105mm can still work, but you’ll generally be closer to the subject. The different distance figures you’ve seen are likely using different reference points: some quote focus distance from the sensor plane, while others mean working distance from the front of the lens to the subject.

Based on the community experience here, a 150mm is a solid choice for insect work, and 180mm can be even better if your priority is extra distance. Optical quality is unlikely to be the deciding factor, since dedicated macro lenses are generally very sharp.

Accessories can help, but each has tradeoffs. Extension tubes increase magnification but reduce focusing range and convenience. Teleconverters can extend reach and may be useful in some setups. One answer reports good results using a 70–200mm with a 2x teleconverter plus extension tubes for bee photography at about 1:1 from roughly 18–24 inches. So yes, these add-ons can be practical, but for a simple dedicated insect setup, a longer macro lens is the straightforward solution.