Ellen I think you are adding 2+2 and making 5!
The point about HRT and estrogen levels is far simpler than you are making out. I don't know why but some people do get hung up on which estrogen is high , low, whatever and it's not that important.
Heavy periods tend to happen in peri when a cycle is incomplete- so estrogen rises but no ovulation takes place, no progesterone is released, so no bleed, or a light bleed, then the next period is heavy. Also estrogen levels can rise erratically as the body tries to push out those last follicles (ovulation.)
The point of HRT is that is sets a constant level, or aims to, each cycle. In early peri then yes, your own levels will rise and fall a bit too.
If you have peri symptoms like flushes, insomnia, low mood, and other stuff, then HRT will help. If you can manage without HRT until your periods have stopped, do that.