So I looked into this myself, and I think I arrived at an answer.
a) According to this website, it states:
According to Ulla, while the Gentiles were given thirty commandments, in reality they do none of them. The notice that they “observe” three of the thirty is tongue-in-cheek, for the manner in which they “observe” them is in reality proof of their paganism. Thus, though they engage in homosexual relations,they do not sanctify such relationships with a marriage contract (ketubbah). Likewise, even though they eat dead meat (and some would understand this even to include human flesh), they do not sell it openly in the markets (they don’t weigh it out).
And so on. Basically, it states that Rabbi Ulla is saying that there are 30 mitzvot given, but that the non-Jews are really doing none of them except for three which they are "technically" observing. So there is no issue with Rabbi Ulla's statement according to this as its merely stating what the non-Jews were doing. Rabbi Ulla was still maintaining the thirty mitzvot statement. In reality, non-Jews are supposed to be keeping all of the thirty mitzvot that Rabbi Ulla is thinking of, but they're actually performing only three unfortunately. It does not refer to the idea that the other 27 mitzvot were abrogated or anything like that.
b) According to Rabbi Moshe Weiner in The Divine Code: The Guide to Observing the Noahide Code, Revealed from Mount Sinai in the Torah of Moses , which is dubbed as the "Shulchan Aruch" of the Noahide laws, having been given a "stamp of approval" by numerous halachic authorities and Rabbis, including I believe two former Chief Rabbis of Israel, he states at the beginning of the book:
Rambam explains in Laws of Kings 8:11: “...The Holy One, blessed be He, commanded them [the Seven Noahide Commandments] in the Torah, and informed us through Moses our teacher that Noaĥ’s descendants had been previously commanded to fulfill them.” This means that even though Noaĥ’s descendants were previously commanded to fulfill them – and this Divine command was not nullified in legal terms, and Gentiles are still obligated by the power of the original commands – nevertheless, there were more details added by God through Moses at the giving of the Torah at Mount Sinai. Clearly, the Noahide Commandments were commanded to Moses, because even though they were commanded previously to Adam and Noaĥ, they were never written down as Torah before Mount Sinai. Their recording in the Written Torah was through Moses, and their explanations and details as transmitted in the Oral Torah were given to Moses, as will be explained. According to his above-cited ruling, Rambam explains that (a) the descendants of Noaĥ are obligated to observe their Seven Commandments because these were commanded to them by God through Moses, and (b) when the Torah was given by God through Moses, there was a spiritual dimension that He added for the Gentiles as well as for the Jews.
So basically the reconciliation is that despite Noah and his descendants being commanded to fulfil the original mitzvot, at the time the Torah was given at Mt. Sinai, additional laws were added (and as far as I can recall, even some non-Israelites/people who didn't go on to become Israelites, like some Egyptians were there, so it makes sense for the Noahide mitzvot to get expanded so that they'd hear it for themselves too in my view), hence why we find the mitzvot of respecting the Torah scholars in there because Torah scholarship (studying the Torah that was given) begins immediately after Mt. Sinai revelation.
In summary, there are more than three Noahide commandments, and Rabbi Ulla was simply listing the three that the non-Jews were performing instead of doing the full thirty that Rabbi Ulla was stating, and respecting the Torah scholars is a Noahide commandment because Noahide commandments despite never being abrogated, were added upon after the revelation at Mt. Sinai. According to Rabbi Moshe Weiner who cites Rambam, this is one of the reasons why its necessary to acknowledge that one is following the Noahide mitzvot because they come from the revelation and not merely from one's personal reason/rational deduction.