The right level for one might not be the right level for another. Doctors really can't know in advance what that level will be for that particular individual at this particular time in their lives. Sensitivity varies from one person to another and changes throughout one's lifetime according to a host of factors. Is 128 or 185 a good level for YOU? You only know, not the doctor, not anyone else, based on how your mind and body are responding. Your doctor should be asking you questions like 1) how are you feeling 2) are breasts growing 3) is skin soft and drier 4) is ejaculate/erections less 5) is body hair growth less. Based on your feedback, they can assess whether your current regimen is effective or not, regardless of levels.
Many doctors will just aim for the average level in premenopausal women, so around 100-200 pg/ml (levels are much higher during pregnancy and lower during the first years of puberty, BY THE WAY) not taking into account the above where this range may be fine for some transwomen in terms of how they feel and overall feminization but not fine (too low) for others who need more to get optimal results.
Also, levels fluctuate, even on pellets. Hence, tests are unreliable in terms of determining the levels at which you are functioning 24/7.
Study after study has shown that bio-identical estradiol, when taken non-orally (even orally), is quite safe, even at higher levels and in populations at greater risk. Hence, aiming for a particular range because of the belief that higher levels may be harmful is just not substantiated.
Food for thought, remain critical.