I was advised to swap my birth control pills from 0.3 estrogen to 0.2 estrogen due to sour breasts and quite big mood swings. does this change have a big impact or it doesn't change too much? is it better to have less estrogen generally?

Although it also depends on the type and amount of progestin that is also contained in your birth control pill, a lower amount of estrogen should help your symptoms. In general, it is best to take a birth control that contains the least amount of estrogen possible to reduce your risk of developing breast cancer, endometrial cancer, blood clots, stroke, or cardiovascular disease in the long run.