Well you’ll need to listen to your needs and your body over anything else, but here is my understanding of the different birth control methods.
Nexplanon - 68mg of etonogestrel released at a time
Micronor (mini-pill) - has 36mg of levonorgestrel per pill
Mirena IUD - releases approximately 20 mcg of levonogetrel a day
While I understand that you have your own reasons for not wanting an IUD, to me it is clear that the progression from the mini-pill to the Mirena is the most logical. I am always nervous about Nexplanon because the bleeding pattern is very uncertain - 1/3 of people end up with no bleeding, 1/3 of people have regular periods, and 1/3 of people have constant bleeding. Because of those odds, I don’t tend to suggest it to my patients. Additionally, the extraordinarily high levels of progesterone causes a number of other side effects like mood swings, depression, hair loss, weight gain, PMS symptoms, etc. However, it is the most effective birth control, so I would rather my patients have the Nexplanon implant than the pill if they truly are looking for a way to avoid pregnancy.
Anyway, I hope that all helps! Good luck!