In response to your first question, I'm pretty concerned that artificial wombs would not be very high impact from a population perspective.

If artificial wombs were very expensive, I suspect only very wealthy people would make use of them, and it would not solve the fertility crisis.

If artificial wombs were very cheap, I suspect the average person would have barely any more children. This is because the primary drivers for the current fertility crisis seem to also motivate people to want to have less children in general.

According to Our World in Data, the primary drivers of the fertility crisis are:

• the empowerment of women — increased access to education and increased labor market participation
• declining rates of child mortality
• rising costs of bringing up children, with the decline of child labor

It seems like the first and second trend will continue for the foreseeable future, and the third trend will continue in the near-time but reverse in the long-term. Notably, the first trend has to do with women's ability to make their own decisions. It seems that, in general, if women can choose how many children to have, they usually only have two or three.

Additionally, according a recent 80,000 Hours interview (which was with a non-expert), one of the major drivers of the fertility crisis is simply that people have more interesting things to do with their time than having children. This trend also seems like it will only continue.

I also suspect that if artificial wombs were very cheap, some fanatical religious groups would have extraordinarily large amounts of offspring, which could be generally harmful to the long-term future.

On the other hand though, I suspect that if there were great widespread economic prosperity and people were no longer required to work (such as could be the case if AGI comes about), the average person may have far more children, which, from a total view of population ethics, would be very beneficial.