Which provision of the 1836 constitution was the most important adaptation of spanish-american law for the texas republic?

The provision that became  the most important adaptation of Spanish-American Law for the Texas Republic was: the idea of community property

The idea of community property conveys that both husband and wife are entitled to half of the assets that they acquired during their marriage if their marriage managed to end.
Back then, The American government also impose a similar 50-50 agreement with the Spaniard Empire regarding the region in the Texas Republic.

Independent executive agencies are more specialised.