There is guidance for things like osteoporosis prevention, which is that it needs to be at least 270pmol + but benefits increase the higher the dose (ie the bone will be built back up again better and faster).
You have to realise the NHS is far far far too ill equipped to optimise HRT for all women, routinely. They just can't cope with that. They can't cope with the regular blood testing which would be required, with the referral for scans that higher estrogen doses might sometimes mean, or with millions of women needing personalised care because of varying absorption levels for all 3 hormones. So they give everyone a ridiculous generic dosage of low levels of estrogen and heavy handed high levels of progesterone and fight to refuse everyone testosterone so they don't need to deal with that at all. Only women who do their own research and learn what to advocate for, might get more what they need.
Most women need their estrogen to be between 400-650pmol for resolution of symptoms. That comes from Newson Health doctors, the several I've seen now. Some women need even higher and Newson say levels up to 1000 are fine. If you increase estrogen you need to be on a higher dose of progesterone as well. (Well, you might not need that - but you'd need to take it vaginally or rectally and test whilst taking it to see if you are absorbing enough. Otherwise it's just guesswork.)
Cardiologists know almost nothing about menopause, most of the time. Which is ridiculous because it affects the heart so much. This is all the effect of women's health being such a low priority... .