In the case of aromatase, its effectiveness increases with weight, age and other specific features such as Klinefelter's syndrome. However, there is non-aromatase testosterone. I think it's dht. On the other hand, if your estradiol is already very high then even if you increase testosterone, and therefore the T/E2 ratio, it won't make any difference to gynaecomastia.
I tried a fertility treatment a few years ago which boosted testosterone production. I reached a very high level but also 68 pg/mL in E2. The T/E2 ratio was very much in favour of testosterone and yet over the course of the treatment (7 months) gynaecomastia appeared and then fortunately disappeared. This was a temporary treatment.
There are aromatase inhibitors but you have to be very careful with them and it's not certain that you can take them for life. In short, if you have an elevated E2 without treatment, there aren't too many solutions.
As far as fertility is concerned, the problem is that if you take exogenous testosterone, your body will reduce the production of LH and FSH because you'll have enough testosterone. But it's FSH that enables spermatozoa to be generated. And if you take it for too long, it's irreversible. So you'll have to take testosterone for life. In general, spermatozoa are frozen before these treatments.