The Gemoro says in Shabbos one should not treat one son different among his sons. Is it proper or not proper to leave in a will a double portion to a Bechor, (first born). On one hand we see that when there is no will the bechor gets a double portion of the inheritance. On the other hand, perhaps that doesn’t create jealousy because that is what the Torah commanded for inheritance. Whereas when it comes from the father’s will to give the Bechor a double portion, perhaps this does create jealousy and is not what Chazal intended. Similarly, what would be the proper outlook as far as the sons inheriting and not the daughters?

See question above. If one was to write a correct will that follows both Halacha and the law of the land, one can distribute his assets in proper different ways as is needed and following the opinion of the competent Bis Din, Rabbi and legal authority, he may also follow therein some of the ways that the Torah sponsors.