Okay, I think I understand the question you asked.
First, the GIRM (General Instruction of the Roman Missal) is the document from the CDW that regulates most aspects of the liturgy. Those aspects which it doesn’t regulate are clearly spelled out as being something the bishop has control over or where the priest/deacon may make adaptations (indicated by “…says in these or other words”). This is non-negotiable.
Redemptions Sacramentum is an instruction which clarifies law. In this case, the law is the GIRM. It has authority over everything except particular law and canon law. This means that, for example, it has no authority to prevent the pouring of the precious blood following the consecration in the United States which is permitted under particular law. Since particular law is promulgatged with the authority of the pope who has to approve it, an instruction cannot override it. (See canon 33 for more on this).
Since an instruction (a document from Rome with a particular canonical weight) clarifies the law, it must be followed except as noted above.
I hope this helps.
Deacon Ed