I think that is a really good question, because the idea that women have power jars with me so I need to try and think through what I mean. I think the second part of what you say is true, but not necessarily the first.
So, second wave feminists argued that sex and gender were different. So sex was biological difference and gender was a social construct. Being born female did not mean that women should be confined to more of the domestic tasks or be paid less; these were differences which were socially imposed because of gender norms (women were seen as more nurturing and caring historically). In other words, gender norms were built on biological difference, but second wave feminists argued that the foundations of this were false. There is no biological reason why a woman cannot do the same job as a man, or be paid the same, there are only social reasons.
At the same time, second wave feminists laid bare other factors of women's oppression such as rape and domestic violence, which were based on biological difference, but also social conventions which saw men as the head of the household and women (still) as his property (physically).
These things meant that for second wave feminism the root of women's oppression was in their biology.
Addressing these issues has meant women have more equality and more choices to leave abusive relationships and be self-sufficient, yes. But I would say that is agency, not power, because structural inequality is still there.
The second part - the shoring up of gender norms - is more complicated. Because I think it comes from neoliberalism (third wave feminism combined with capitalism) as much as men - so it does not work in the same way as second wave feminism sees men as the oppressor class. The technologies of power (the way power works) are less obvious and more insidious. So third wave feminism was about performing gender, embracing female sexuality as a form of empowerment and one's gender identity as something one could create and own. I think (and I am not an expert) it started off as a way of exercising agency but was co-opted by neoliberal capitalism as a way of making money (femininity could be packaged and sold). What we saw in the early 2000s, if not before, was a very clear gendering of lifestyles and products.
So whereas in the 1970s things were much more gender neutral, e.g. children's toys/clothes etc, by the 2000s, they were clearly gendered. This extended to adults - at one point, I realised my bathroom was a sea of bright pink.
The third thing was then what I call the erasing of biology. The trans argument that being a woman is external and an identity one can choose; in fact, referring to periods and pregnancy is seen as transphobic (despite the fact that these things were the reasons women in the past were confined to narrow social roles). This is the antithesis of what second wave feminism argued and why the TRA argument is with second wave feminists. However, the root of trans I think is about escaping one's socially imposed gender role, not biology. But the way to escape gender is configured as taking on the gender norms of the other sex, not by dismantling gender norms.
It works to shore up gender because the confines of what it means to be a man have narrowed - if men want to wear make up or do more socially-constructed female things, they must be trans*. It enforces a much narrower view of masculinity (shoring up gender norms) than was apparent, say, in the 1980s when men could wear make up and be more androgynous. And correspondingly, the idea of what it means to be a woman is narrowed down to external ideals of femininity (it is no accident that Caitlyn Jenner was Glamour's woman of the year, a trans woman can be a better ideal of a woman as she is essentially being created)
I don't think it is about women's power, because transwomen don't give up the power they had by being born male. That is not possible as male privilege (the way boys are treated differently from girls) is inscribed from birth by society. I don't think they get women's power either, as women don't have any (they just have agency, which is the ability to negotiate structural barriers and cultural norms as individuals; power would be the ability to create those norms).
In fact some transwomen are exerting power by very publicly defining what it means to be a woman.
Which comes back to the point that (natural born as oppose to hormonally or surgically constructed) biology is being erased as (socially constructed) gender norms are shored up.