Parshas Beraishis:The Mitzvah of Peru U'revu

Last Shabbos I gave my chaburah on the obligation of peru u'revu. I mainly focused on whether women and b'nei noach are obligated in this mitzvah. I have already written about this topic over here, so I won't add much. I will just add that I believe the lomdus is based on how one understands the nature of "lo tohu bera'a, lasheves yatzarah". Is this an independent mitzvah besides the mitzvah of peru u'revu, or is it part of peru u'revu and is the reason why peru u'revu is a mitzvah rabba.

One nafka mina would be if someone already was m'kayeim peru u'revu, would there still be a mitzvah of "lo tohu bera'a, lasheves yatzarah". If they are two independent mitzvos, then one could argue you still get a mitzvah for having more kids.
Another nafkah mina would be that even though women and b'nei noach don't have a chiyuv of peru u'revu they still might have a chiyuiv of "lo tohu bera'a, lasheves yatzarah"

This seems to be a machlokes rishonim. Tosafos in Gittin 41b asks 'why did the gemara say you must free an eved because of "lo tohu bera'a, lasheves yatzarah" , why don't we say we should free the eved so he can be m'kayeim the mitzvah of peru u'revu? Tosafos gives 3 answers., one of them being that an eved has a chiyuv to have children because of "lo tohu bera'a, lasheves yatzarah". The Chasam Sofer understands all 3 answers of Tosafos as saying that "lo tohu bera'a, lasheves yatzarah" is an independent mitzvah from peru u'revu. Others like the Chelkas M'chokeik in Even Ezer Siman 1, learn it is a machlokes within the answers of Tosafos.
Tosafos in Chagiga 2b seems to learn it is all one mitzvah.

I think one can possibly be m'dayeik in the Rambam that he holds "lo tohu bera'a" is part of the mitzvah of peru u'revu. The Rambam paskens that a women is patur from peru u'revu. If lo tohu bera'a, lasheves yatzarah is an independent mitzvah, shouldn't he write that women are chayav because of this reason? Furthermore, the Rambam writes that even if you have been m'kayeim peru u'revu, there is a mitzvah m'divrei sofrim to have more children in order to bring more Jews into the world. Why didn't the Rambam write it is a mitzvah because of lo tohu bera'a, lasheves yatzarah? Possibly, the Rambam held lo tohu bera'a, lasheves yatzarah is part of peru u'revu.