About 15-20 percent of women continue to have menopausal symptoms long after menopause, although they should diminish in intensity with time. There have been many research studies on non-estrogen treatments for menopause (black cohosh, soy products, dong quoi and other herbs) that have not proven effective in treating symptoms. That said, some individual women have found them to be helpful, but we don't know if that is just a function of time passing.
Estrogen repalcement therapy (HRT) like Mimvey is very effective in treating the symptoms, especially night sweats and hot flashes. There are no studies that show improved cognitive function but many women feel better overall on HRT as they go through menopause. There have also been no important studies that looked at estrogen and cardiac palpitations or arrhythmia.
It is common for women to have palpitations around menopause and the physiology involved is not well understood.You are correct that menopausal symptoms return when HRT is stopped. By weaning off slowly, many women can stop estrogen and be symptom free. As you have discovered, every woman is different and there is no "one size fits all". Some women breeze through menopause without symptoms and others find it very difficult. I hope you can find a doctor who will work with you individually and tailor treatment to help you with this time of life. Over time the body adjusts and you will feel great again.